i was talkin to the guys at Murray's in Ann Arbor, and they said that the Red Line and Chevron stuff are ok, but the best stuff for cleaning injectors is Lucas Racing's injector cleaner, it's the strongest cleaner out there, it's got an injector lubricant in it, plus it's $2.99 plus tax, which is between 1/3 and 1/4 what you'll pay for Chevron or Red Line

 

Thanks, but I had my injectors cleaned (by ultra-sound), so that shouldn't be an issue...

 

you will need to ohm the sensors because the stock ecu only sets codes for shorted or open. so if the water temp sensor is reading an ohm value of -40f it will add a ton of fuel to the car. check your fuel pressure. you check the fpr most easily by pulling the vac line off it and seeing if there is fuel in it. you should be able to reach it if you have a down pipe from under the car.

 

mad_7tist:
Yes, I plan to meter the sensors resistance. Altough, I have one question about water thermosensor... Do you need to remove, the water pump housing to locate this sensor? Because the thing is, that I received new engine with some stuff already bolted on (t-stat, w-pump, flywheel, coolant lever sensor...) and we never took the wpump housing off. If that's so, then I probably have fresh sensor. I really need to remove the pipe from the y-pipe, so that I can see where is it. I could not define where exactly this water thermosensor sits from the workshop manual... Maybe someone has a picture of it?

Well anyway, in case I have this sensor new, then I can only check the air thermosensor and wiring harness for both. Since this sensors work by resistance, I probably only need to check for 12V coming from wiring harness, right? Also, I read somewhere, that when reading resistance, you need to distract the resistance of the voltmeter from the read value. Is this true?

Anyway, I have some work to do

Good advice tough on checking the FPR. I will try to reach it under the car. Are there many lines connected to it? And will I be able to cut the tie-wrap on the vacuum line? Also, what can I expect? Fuel pouring out of it, or just fuel odor smell? And how does FPR leaking affect fuel pressure? Can FPR behave sticky? Because pressure is probably good once in boost, since it pulls nice and smooth from any 2000 to 4500, once it starts pulling. The problem is only in the initial hiccups before the acceleration... Also, if someone has time, can explain how this fpr works? Something like actuator?

 

the fd runs a 5v rference for the sensors. so yes one side of the connector will have 5v and the other will have a good ground. to check the meter you just take a ohm reading by crossing the terminals together and see what the readings are it will be very small. nice meters will allow you to zero them. look at the tps make sure it moves smoothly. check your fuel pressure. when you pull the single vac hose off the fpr if there is any fuel in it it is bad. the fsm has the temp corrected values for the sensors.

the fpr is a restriction the the fuel return line. pinch the return, the injectors see higher pressure. the fpr works by allowing fuel to return at x amount when under vacuum, low pressure, and less fuel to go through the fpr at low vac or boost conditions, high pressure. there is just a diagphram that moves and will restrict the flow. the fpr solenoid will cut the vac to the fpr at hot startup to help with idle quality and vapor issues for like 30sec.

 

mad_7tist: Thanks for the explanation on the fpr and other. If it's just diaghpram with fuel passing it, then there is no way it could be sticking, right? Since there's no oil in the fuel, and it cann't gum up? So if it can fail on one way only, that is with leaking, then how could this result in bucking? And it does buck only at the beginning of throttle movement, which would indicate my fuel pressure should be ok. I will have it checked anyway...

all:
This is what came with my engine:
http://www.parsek.si/documents/soru/...ne_sensors.jpg

The sensor on the t-stat housing is coolant lever sensor. I'm almost 100% sure, there weren't any other sensors attached. So, there probably wasn't any water thermosensor attached, and we used the old one. Can someone show me on this picture, where should it be attached? Thanks.

One more thing, you need to know. My gas mileage is not so good, around 14mpg, some boosting up to 4500rpms, some city driving. It's not that bad, but maybe it is not unrelated? What do you think guys?

 

Is this the waterthermosensor?

 

IIRC the black sensor back there is for the fans and the green one is for the comp. dont have the book here... a bad fpr will allow unmetered fuel into the car. never a good thing

 

I checked the workshop manual (cooling system, E-16) and I'm almost sure it's the green one. It's not a very detailed picture tough.

Anyway, some update: I've rechecked the TPS, and it's perfectly adjusted for narrow range (0.84-4.98V) and full range (0.39-4.42V). I've also checked for dead spots and found out that both ranges are perfectly linear...

 

I have this problem too. Car drives well, especially under load on the freeway. But sit at a stop light for awhile and the car gets worse, more popping and backfiring until it runs rough and dies. After the car cools down it starts right back up. I adjusted the TPS to spec but that's not it. This is a good thread though because the water thermosensor is next on my list, then the intake air sensor. I'll report back.

 

all: My update. I ran out of time to do all the stuff I planned. I had some other things to do... I figured how to read error codes on euro fd's (they don't have MIL or CEL) and got 40 - purge control solenoid... So I removed it and tested it, but it works ok. In the workshop manual it says this one could be causing such behaviour. It controls the amount of fuel gases entering the intake. But I hardly believe this would make the car run soo rich. It's just gases... Anyway, I've cleared the errors, and will read it again today, if there's anything that's ecu giving out. But I really doubt these problems are connected in any way...

Anyway, I was trying to remove the water thermosensor, but I was in a hurry, when I figured out that alternator has very minimal slack on the belt, so I couldn't easily remove it. So I decide it to do it next weekend, when I have more time. Anyway, some said I will need to remove the t-stat housing, but I don't think that's necessary. If there wasn't that nipple on the t-stat, then even the alternator wouldn't have to be removed. I didn't even try to look after the air intake thermosensor...

luizajeff: Great, please post your progress. My doesn't die, but other symptoms are similiar. Did you ever replace FPD or FPR? Maybe you can help us elimante some suspects...

 

Well.. I have this same stupid problem. I noticed every time my bucking happens it's at 2k rpm and my A/F gauge goes to Lean. Like a fuel cut or something. I did rewrap my Harness, when i replaced the engine, so maybe the The Intake sensor got the wrong connector, or it might be bad.

I replaced my Watter Thermosensor and the problem is still there. Injectors are cleaned by RC engineering, all emission stuff is removed with Resistors in place of Connectors. New engine, turbos, open exhaust, ecu etc. No check engine light.

Can someone tell me the colors of the wires going to Intake Sensor, so i can make sure it's right.

Amel

 

Their are a lot of guys who have a similar problem. I believe its just another variation of the 3K. I have a volt meter connected to my 02 sensor and it goes lean when its acting up. I have done every thing I know so far nothing seem to fix it. I run with out my 02 disconnected and use a Apexi fuel computer set to lean out all the ranges except the area where my car acts up. I have a street port and with the low vacuum it just runs far too rich without the Apexi set to lean out the system at least 20%. I have a small harness with a diode set up to stop any spikes going back to the ECU when the solenoids turn off. I haven't placed it on all the solenoids as yet but I did wire it to the air pump and it didn't help me. I have seen a lot of EFI systems use diodes connected to the a/c clutch just to stop spiking back to the ECU.

 

Well, the thermosensor has been ordered (1 of 4 possible sensors, OK 3 because I have a manual) and I will install and test ASAP. I doubt it's my IAT because I get a good voltage reading on my commander. My ignorance though, what and where are the FPD and FPR? I will check them too if this thermosensor doesn't correct.

 

For me, this is absolutely not a 3k hesitation problem. I had that before I replaced the ECU with the PFC, then it went away completely! I put a 2K-3K miles on it before this problem. I've replaced the O2 with a new one (even though it's narrow band) and adjust my TPS which is to spec. I don't think it's my injectors because I use injector cleaner every oil change and the problem is consistent with temp increase. Car starts normally when cold or warm but stalls out when hot. Let it sit and cool down (15-20mins) and then it fires right back up until it gets hot again. Something is not correcting for higher temps. Anyway. I will report back and make a full write-up once resolved.

 

jeff you have a pfc? so look at the temp readings and see what they are on the pfc. you may have a tuning issue. the fpd is located on the firewall side of the primary fuel rail. the fpr is on the secondary fuel rail

 

luizajeff: I see. What are 3 other suspects of yours (the sensors)? FPD is fuel pulsation dampener ($115) and FPR is fuel pressure regulator ($125). Both of them are deep under the UIM and require quite some work to replace them :-/
However, I'm also ordering a bunch of stuff iat, coolant temp sensor, and some fuel system parts... I will be replacing them one by one... First, coolant, then air sensor... If this doesn't help I will go and dig into fuel system...

 

Well, all the temps indicated by my commander are good. This stumped me when I started having the problem. I've monitored all the voltage readings from cold to hot and they all appear within spec (ref. manual). And again, I made no changes to my PFC for 2-3k miles before the problem started. I had it tuned a little rich but not that much, and idle was leaned some for smooth ops. Also, I've tried making some changes with my PFC to see if they might be the issue but no change in symptoms. I'll try the sensor anyway, especially since many other with identical symptoms have corrected theirs by doing so. BTW, thanx for the terminology and clarification. At one point I didn't know what you all meant about IC either.

 

Sorry I was not aware your were running a PFC.
I am assuming when you say it stalls out it wont restart or if it does it runs real poorly. There are some electronic parts which can react to heat and fail. I did drive-ability work for 20 years and that was an everyday thing for me. I would look at the crank sensors, coils and ignition module to start. If you are running the fuel pump voltage regulator that would also be on the list. I often used water to isolate parts which failed in a hot engine. Get the car to act up and pick a system to concentrate on. Spray some water on the component and see if the pattern changes. If the engine wont start, well isolate the sup-system by testing through the fail periods. Check fuel pump pressure, spark and injector pulse. Look close at all the grounds and power inputs. Resistance at those connections often can cause a problem after driving and not on a cold engine.

 

Some new new toughts on my problem: After it's been sitting over night, and I start and drive off in the morning, it takes about 3 minutes to start showing this bucking signs. Could it have something to do with emissions (cold start,...)? I don't think it would be heat specific, because in 3mins the engine is still very cold...

 

In 3minutes, rotaries gets hot

Btw. I have an AF gauge that I can lend you so you can see if you fall on the lean or rich side when the bucking happens.

Lean condition would probably mean problem in fuel components (or a faulty component that reports to the ECU to cut fuel).

Rich condition would mean ignition problems.

 

Not really. Coolant is still below 30C... And the UIM, I-elbow and y-pipe are still cold enough you can teach it without screaming in pain

This is exactly how I was thinking. I'm going tomorrow to do the on-road wideband test (@rsr) and I hope he will also be able to read my fuel pressure - under load on dyno. This two bits of information will probably be very helpful at debugging these problems...

 

When I was doing drive-ability work the most common reason for hesitations and or loss of overall power was ignition related. Since you characterize it as bucking and I own a 3rd gen I feel its less likely to be an ignition problem. We have basically two main plug wires feeding the engine and if one left the building you would be able to here a huge change in the exhaust tone. You can use any digital volt meter to view the 02 voltage. Just tee it in the 02 line and ground the other lead. Use a low scale, 2 volt is fine. The 02 sensor can only see oxygen in the exhaust stream, so when theres a lot of oxygen the mixture is assumed lean and the voltage produced will be on the low end. It might read .1 to .3 volt. It could read .225 depending on the scale. Surely under 1 volt . A rich mixture tends to use up all the oxygen with an excess of fuel left over and produces a higher voltage. A reading of .9 or .930 etc. This will narrow the field. If theres a problem seen you will need to surmise what the injector pules is. You can do that by taping into an injector ground path to the ECU. Again using a volt meter on 20 volt scale. The reading will be just a real time average on the meter but it can be compared with a reading at W.O.T. Again a higher voltage reading would indicate a leaner or shorter pulse with. The lower the voltage the longer the pulse and more fuel being injected. Theres always the reading of the injectors amp draw during the event. This could help you determine if theres a shorted injector or just one which is demanding more than the system can deliver. I don't know what type of injector drivers are in your system but they are likely peak/hold type. They are designed to carry a certain amount of current anything over a set limit will cause the driver to open to protect the ECU. Its possible the coolant sensors have a bad algorithm but its not as likely. Surely its going to improve the input sensors accuracy but maybe not the root cause.

 

soru have you looked/changed the coolant temp sensor yet?

 

J.S.J.: Thanks for advises. I will try some of this over the weekend.I agree with you, that it's probably not ignition. Reading on the net, I got feeling that ignition problems usually develop as hesitations in higher rpm range. My fd seems to feel very comfortable there. Also, without ignition I would presume the right a/f mixture wouldn't ignite until reaching exhaust -> therefore popping and backfiring from exhaust. But in my case, I don't get backfire when bucking, so I presume it's momentary lean condition causing this bucking.

Can I ask you something, how come you do not suspect fuel pressure? Is it impossible, to have such fuel pressure fluctuation, that would be causing momentarily lean condition?

I just got an idea... maybe I should check my fuel pump voltage... Is it possible that for some reason it wouldn't be getting 9V (some resistor failure?) at low speed? For example, at one time the voltage would drop to 5V causing low fuel pressure resulting in lean a/f and bucking... but when I increase the throttle (with clutch in), it usually goes away and starts accelerating and boosting at once. Maybe this is because the ECU or FP relay bypasses resistor and sends 14V to fuelpump?