arec2001

This one really has me stumped.

I obtained a perfectly good running 87 GTA 3 years ago. Soon after buying it the 700R4 let go, and the car sat around for awhile until I finished the T56 conversion last week (some projects just take a while). In that "while" I rebuilt the engine because I thought the head gasket had also let go, turning out it was only the intake leaking. Oh well. Engine had 225k anyways, time for a "freshening up". Rebuilt it back to stock for the exception of Edelbrock headers.

Ever since I got the engine rebuilt it runs like crap. The idle is rough, part throttle is decent, ( <25%), but any more and it seems like it's got no power. What happened? Even if you floor it standing still (in neutral) it cannot go over 4000rpm! And it doesn't sound like a rev limiter just "runs out" at around that rpm. I mean TPI's aren't revvers but I know this thing can reach 5250 easy.

I hooked up a scan tool and all the sensors seem to be giving valid data. I can't get the MAF over 80grams or so but I don't know if that's because there's insufficient fuel.

I hooked up a pressure gauge; it's running 45psi without the vacuum line; 38psi with it on. While driving, it'll flutter around 45psi when you get on it over 25% throttle.

Any ideas? I don't want to blindly start changing components.

Oh yeah, there was one more thing i did change during the rebuild. It got a hypertech adj fuel regulator. Maybe it's bad? How can i tell? I can't seem to find my old one

Thanks in advance for any and all help,

arec2001
87 GTA 6 spd, stock

bjankuski

Check for a clogged catolitic convertor or some exhaust restriction. My 1987 GTA 350 had a clogged cat and it would not rev past 4750 and ran 16.20's when I bought it. I fixed the cat and the car would shift at 5250 and ran 15.15's.

zimmer

clogged converter. It happened to me too.

nblanchard

I thought mine was a clogged concerter, turned out to be my ECM was toast (even though it was throwing a code 12 still)

A converter can go just from excess moisture.

Have you tried a wide open throttle voltage check on your Throttle Position Sensor?

arec2001

No catalytic on the car. It's got a Flowmaster Force 2 exhaust, doubt it's clogged; at least it better not.

Yes, checked TPS with scan tool. Full range works (0 - 100%).

Any other ideas, anyone?

nblanchard

Well... now its just a guessing game for me Only thing I can think of is base timing or the Knock Sensor, both things you can check yourself.

You said the MAF doesn't go over 80, I would look into a new MAF possibly. too bad you're not around here, I have a spare.

mtccl

Start from scratch on your base timing. If you had the distributor out that may be the problem. Use the TDC rotor pointing at the #1 cylinder cap wire method. Don't forget to bypass the ESC by disconnecting the tan and black wire on the passenger firewall in the engine compartment.

85transamtpi

Is the scan tool picking up any knock retard?

arec2001

The scan tool picks up knock sometimes during startup, but never while driving.

I'll go out there and time it from scratch again.....

...and FYI every once in a while, soon after startup, if you mash the throttle, it'll momentarily act like a Qjet carb (where it hesitates as the secondaries open), then the power will hit, only for a fraction of a second, and then die off. I'm going to see if I can record that event with the scan tool. I'm going to also see if I can be watching the fuel pressure as that happens, but that may not be easy.

Is it easy to bypass the fuel filter to see if it's clogged? Maybe the injectors are real dirty (I do remember them not looking very good and they are the stock injectors and did sit without fuel pressure for years...)

....also the car cannot maintain fuel pressure when off (after 10 minutes its at 20 psi, but I can't find any leaks)....

nblanchard

If your MAF numbers are low, it has to be your mAF

ploegi

Disconnect the MAF, and see if it runs any better. It will set a code, but, it can run without it. Just drives kinda odd.....

85transamtpi

My '85 was running similar and giving me a MAF code from time to time. I'd try a new burn off relay and if that doesnt work its MAF time . That could explain the strange readings you are getting with your scan tool, and the strange way the engine is acting. Have one of your buddies with a thirdgen let you try using their MAF and see if that clears up your promlem.

No knock retard and problems reving could easily be your MAF or relay.

Good luck

irocnroll89

iTrader: (4)

i dynoed my car the other day, and on the second pull it would not rev at all over 4000. I found out the distributor wire (tan) for ignition advance was not connected....... I had forgotten to hook it up after changing my base timing. Let me tell you those headers got red hot. Third run was awesome. This is only a suggestion. good luck and keep us posted.... SHAGGY

arec2001

It does set a code 36 sometimes, and I've had nothing but problems with the MAF relay / burnoff connectors. The wires (at the relay connections) aren't doing so well. But if it is the MAF, I'd much rather switch to a '730 PCM and MAP than buy a MAF. Then I can get rid of that restrictive intake and that overpriced sensor. It's just I'm not going that route until I'm pretty sure the MAF is the problem. Remember, the MAF is tracking airflow pretty well at low numbers. I don't know. Maybe the whole system needs to be shot.

I have no friends who have a thirdgen. Actually, I have no friends who have V-8's in the area This would be much easier when I lived in Memphis or in Detroit.

Anyone live in or near Orlando, Florida?

arec2001

OK, here's the latest,

I disconnected the MAF relay and now it just simply dies (like fuel shutoff) when I mash the throttle. I though well it must be fuel pressure.

Hooked up the pressure guage and it stays constant at 45psi (when on the throttle)! Wouldn't it lose fuel pressure if it was starving for fuel? And i mean it feels like complete shut-off.

I hooked up a scan tool and the "shutoff" happens when the pulsewidth is greater than 10ms. It seems once it hits the 10ms width it just dies. Bad injector? But how could one affect all 8! I understand how it could affect one bank (4), but all eight!

Help?

camaro-mayhem

you say the injectors are dirty possibly,have you put fuel injector cleaner in?im still not very good with fuel injection,sooo...just my 2 cents

ZZ28ZZ

Timing chain off 1 tooth?
Notice the distributer now being at a different position than before to achieve proper ignition timing?
Did that once, could have swore I had it right!

ZZ28ZZ

Timing chain off 1 tooth?
Notice the distributer now being at a different position than before to achieve proper ignition timing?
Did that once, could have swore I had it right!

arec2001

PROBLEM SOLVED.

Its been months and months and now that I looked up this thread again to close it I noticed someone had already guessed it.
Actually, I've had this problem since Nov of '99

I rebuild the engine under *extreme* duress (ie had to be running yesterday) and had my timing chain 46 degrees of crank rotation advanced!!!! Amazing the thing ran at all! And to think I drove it like that on and off for four years!

I basically lined up the cam dot with the keyway dot, not with the actual "0" dot (I put the cam in straight up). I guess stock pistons have a lot of clearance, since at the non-compression TDC the intake valve was open .2"

Nevertheless the car run much much smoother now, idle is fair but not perfect (which is should be with w/ stock peanut cam). Vacuum is higher but still fluctuates between 18-20". I'm guessing either a valve is sticking (from running so advanced, it was dumping exhaust back into the intake) or burned. Time will tell, I hope, if it goes away.

For those who want to know, here's a simple way to tell if you cam is installed incorrectly (I mean way off):

I noticed that my intake air temp is much cooler. Before, my intake air temp would stabilize with water temp (195) after about 10 min of operation. Now it runs at 115 degrees after hours of highway driving. It seems that exhaust will heat up that plenum rather quickly!