I just searched 25 pages on the board but couldn't find anything like this. I remember reading something about it but I can't find it now... anyway...

I just put my rebuild in my 87 GXL. I had some problems getting it started but it finally came to life and idled beautifully at about 1500 RPM's. I had adjusted the idle screw on top of the intake a few turns to make it idle high on start-up. After about an hour of run time I turned the screw back to about a closed position and the RPM's won't go below 1100??? So that's number one.

Second. At 2500 RPM's I lose power (and RPM's) and get a weird honking sound from the AFM. I checked the flap and it moves freely but I think it's opening and closing really fast in order to make the duck-getting-stepped-on-like sound. Why can't I get more than 2500 RPM's out of it???? Why no power????? Vacuum related?? TPS?? I saw the thread about losing power at 3500 but it didn't seem to be the same thing I am experiencing. All ideas and help appreciated. Thanks!!!

 

Guys, any thoughts???? I need to get this baby runnin smoothly tomorrow!!!!!

 

Lets look at the idle problem first. There are 2 things that adjust the idle (well actually 3) for the N/A. First off, make sure the initial set connector is jumpered for ALL idle adjustments. Second, the variable resistor affects your initial idle, as well as that air screw on top of the TB.

Why am I so interested in idle? Unless you get the idle down in the 800 rpm range, you CANNOT accurately time your FC. If you cant get it to idle down, you have a vacuum leak, and thats probably the source of your problems.

Check everything out and get back to me.

Jarrett

 

Thanks J-Rat

 

I am getting the same "honking" sound, but I have a nice idle. I have almost no power/ acceleration and the car starts to shake at 2500 rpm while driving, I can get up to about 40 MPH in 5th. I'm afraid I've blown a rotor, but would like to hear some other possibilities (I will try wiring the 6 ports open to see if that helps). I smell gasoline in the passenger compartment while driving. I do know I have an exhaust leak just after the exhaust manifold, maybe in the cat.

Any help appreciated.

 

OK. I've checked everything. Got the idle down. Cruise control cable was too tight. Timed it and the timeing was right on for leading and trailing. But I still have no power over 2500 and I still get that damn honking sound from the AFM. I re-checked the vacuum connections, at least the ones I could see and get to and they seem to be in order. Electrical are fine also. What's next to check??

 

For what it's worth:

I assume you see no power past 2500 rpm when you slowly depress the accelerator pedal.

check if you have a restriction in the intake. Maybe the secondary plates are not opening properly. Check the double throttle system (see FSM).

fuel system maybe (pump,filter,injectors).

clogged exhaust maybe (see if runs better if you remove the o2 sensor)

Hugues -

 

Doens't matter how fast or slow you depress the accelerator. All the plates open fully when pressed wot. The fuel filter is new (yes it's on correctly). Injecteros were cleaned and tested at Cruisin performance. I will try the O2 sensor. I am getting good exhaust out the back so I don't think it's clogged. Thanks for the ideas Hugues.

 

Okay, this one is odd. REcheck your intake tubes also, make sure that they are seated and tight... I am starting to wonder if this is a fuel/AFM problem...

Possible that the fuel lines are crossed? Is the pressure regulator hooked up? Also, might want to check the voltage at the fuel pump.

Jarrett

 

Don't wire open the ports. Have you done a compression test?

To the original poster, a "honking" sound to me indicated a vacuum leak just after the AFM. Make sure that accordian tube is all the way on, and the clamp is tight (they like to work off).

 

HAve you tried spraying carb cleaner, looking for vac leaks?

 

No J-Rat. Just spray carb cleaner under and around the upper intake and look for an increase in rpm's?

 

Here's suggestion, is your throttle cable snagging up on something?

 

Yup...Vac leaks allow unmetered air into the intake path, causing a lean condition. If you spray carb cleaner on a vac leak, it changes the mixture temporarily, and will cause the idle to surge.

Keep a fire extinguisher handy!!!

Jarrett

 

What happened to the rest of the posts??????????????

Oh well... any other thoughts guys??? I'm at a loss

 

Oh they were edited out ... thanks Ice

 

Did you try disconnecting or checking the TPS?

 

Not yet, but that's next. I saw your post and the link about the TPS. Going to try that next.

Good luck with the engine. Those compression numbers looked real low. New should be in the 100 range... 100,000 in the 80's Anything below 70 aint looking good.

 

1adzom,

One other thing, make sure you break her in right.

I don't think you're supposed to bring the car above 4 grand for the first 1000 miles or something on rebuilds.

I know that there's real factual info on this and I'm going from memory, so becareful it may just be a break in period thang.

 

Thanks Templeswain. I know you shouldn't go above 4k but I can't even get it above 2500 and it looses power at that.

 

Compression test it man, if your having any bad problems like that you should always test compression.

 

Thanks Mephis. I'll check compression tomorrow. But here's a new bit of information. If I creep up the rpm's from idle i can get to 2500 sometimes 2700 with no problems. If I go from idle to wot all at once it will exhibit the same symptoms as it does at 2500 but it's immediate. Maybe that helps with the diagnosis??????

 

That's what mine does only I get to 3700RPM before the Braaap (even w/tps disconnected). I also pulled the plug on the BAC hoping that would cure it, but it just dropped the idle a little. I pulled the accordian and plastic piece off the throttle body to inspect the operation of the throttle plates and they seem to be working properly.

 

Guys check this... If I creep up the rpm's from idle i can get to 2500 sometimes 2700 with no problems. If I go from idle to wot all at once it will exhibit the same symptoms as it does at 2500 but it's immediate. Maybe that helps with the diagnosis??????

 

I am just realizing we are talking about a freshly rebuilt engine.

How long have you let it run idling ?

It's gonna take a while to break in and build compression. Unless it's broken in properly, no point adjusting TPS, idle, etc. Just let it idle at 1,200-1,500 for a while by adjusting the little 8mm nut on top of the intake (the 1 with a lock nut).

edit:
go to www.rotaryresurrection.com (kevin landers site) under tech for proper break-in procedure.

hugues -