I'm having an absolutley terrible time with my car - 87 LB9 . It hasn't been right all year and I've just about had enough of it. I'm so sick of it I could give it away.

My problem is it had absolutley no power. I thought it was an ignition thing and replaced the cap/rotor/wires as they were done anyway, but it made no difference. I've tried it with and wthout the MSD box and no difference. The spark plugs were replaced at christmas (car wasnt 100% back then either), the O2 sensor was replaced about a year and a half ago.

Here's the symptoms. If I'm driving at low rpm and floor it, the car will drop revs and die. If im driving oin the highway and floor it it is sluggish and picks up a little when it gets about 3000-3500rpm, which makes me think it's not fuel starvation? If it's in the drive way and I rev it when it's at 2000rpm it will rev up fine, below that and the rpm drops and it can cut out.

Only thing that makes me wonder if it's an injector is the fact the the pass side header where the 4 go into 1 is, glows red and from what I can see the drivers side does not. A few months back when it was running better you would floor it and there wouldbe black smoke from the exhause which also suggersts running rich.

I'm going to put the stock chip in tomorrow after work and see if that makes a difference.

Anyone got any ideas as to what it could be? I'm not wanting to start throwing money away by replacing perfectly good parts.

Sorry it's such a long post.

Robert

 

Man, this isn't going to be much help for you, but I'm having the same problem right now. I don't even know where to start now. I have a new set of wires, good plugs, dist, and rotor. I checked the TPS and looked for Vacuum leaks. I just don't know. Hopefully I'll get to mess with it some soon. I'll let you know if I happen to figure out the mystery.
Good luck
FBird

 

I went out today with an O2 guage connected to the O2 sensor. Not the best, but all I have. With my custom chip it was running way rich. I put the stock one back in and I would say it ran a bit better. No power off idle still, not much under 3000rpm but pretty good after that. Thing is I've been using the aftermarket chip for about 2 years or so and I've had no problems.

Ran the scanner with the stock chip and the Block Learn was 146 which suggests to me that it's adding fuel.

Before I swapped chips I started the car and it was leaving 2 black patches on the ground where the exhausts turned down.

Another thing. If I sit at a dead stop with my foot on the brake and put my foot on the gas, it's difficult to get the engine to climb the RPMs. Infact, it's imp[ossible to launch this car at the moment, it's useless and I've just about had enough of it.

I'm going to try and do a fuel pressure leak down test tomorrow.

No one can help me with this one? Please?


***Edit***

The engine has been modded with L98 vette heads, cam, rockers, intake, headers, etc. But has been running fine the last 2 years.

I did have a bronze distributer gear on the distributer which wore out and had to be replaced with the stock one. It was a garage that did the replacement.

Just trying to give as much info as possible.

 

Could it be that the timing marks have somehow moved and the timing is way way retarded?

 

With a piston stop, you should be able to verify the timing marks, or at least get them close enough for argument's sake.

The pressure test might yield some good information. The fact that the stock PROM make s difference is a little troubling, however.

 

Check your 2 "ECM" fuses in the fuse block.

I'm guessing the "ECM 2" will be blown.

 

Can you explain this one a little bit, you left me curious

What all is on the ECM 2 circuit?

 

where are the 2 fuses located? I know about the one on the pass side fender.

 

TPI is a "batch fire" injection system, where the injectors are fired all together. Although actually, they are in 2 batches, a left and a right; each with its own driver in the ECM, and its own fuse. ECM1 IIRC is for the left bank, and ECM2 is for the right bank.

At least in some years that's how it's set up.

The fuses are in the fuse block at the driver's left knee.

Just a wild guess, based on your description that matches a severe lean condition, and the right bank in particular is drastically lean (glowing headers); but....

"The simplest explanation that fits all the facts is usually the right one."
— Occam, ancient Greek philosopher, from the days when FI systems were entirely mechanical

 

OK, I see. On my 87 it's just listed as INJ1 and INJ2. Had that exact problem when I got my car, and low and behold, it was missing the inj 2 fuse. Ran like crap...

 

Sorry I haven't gotten back to this one, I've been so busy the last week. I checked the fuses and they are good. I checked the resistance of the injectors and came up with the following:

1. 16.3
2. 16.3
3. 16.4
4. 16.3
5. 16.3
6. 16.2
7. 16.2
8. 16.3

I did a leak down test too and only lost about 10 psi in the space of 20 minutes.

I'm wondering if it could be the O2 sensor as the problem seems to be when the car is in open loop. I'm also wondering if it could be a problem with the plugs?

The car is running so rich, it's either pumping more fuel in or there isn't a good enough spart to ignite it?

Another idea I'm having is....I've been messing about with governer gears in my new tranny and as it is at the moment it upshifts early. I'm wondering if it could be a mix of things? Maybe upshifting too early at WOT and late a part throttle causing more fuel to be pumped in at lower revs? When cruising I have to have the pedal almost at the floor to shift from say 3rd to 2nd. Wondering if the TPS is thinking more fuel, but the tranny is keeping the revs down so it's not being used?

Just some ideas.

Thanks again for any help


Robert

 

The glowing header thing made me think clogged cat. The rich condition made me think Coolant Temperature Sensor (It is different than the coolant gauge wire).

 

For kicks get your ignition module checked. The resistance is good.
How are you setting and checking the timing?

Some other reading (scabbed from Vader) (so you can verifyopen v closed loop):

Field Service Mode will display some basic ECM information via the SES lamp. If the ECM is in Open-Loop mode, the SES light will flash rapidly, about 2½ times per second. If it's in Closed-Loop mode, it will flash about once per second. When in Closed Loop mode, flashing less than once per second indicates the ECM is enriching the mixture above the 128 count base line. Flashing more than once per second indicates the ECM is leaning the mixture below the 128 base line.

Inserting a 3.9K ohm resistance in the diagnostic request pin to ground will invoke Factory Test Mode or Backup Fuel and Spark Mode ("Limp Home Mode"), which forces the ECM to use predetermined fuel calculations in the ECM PROM instead of the learned inputs in active RAM. Backup fuel is usually around 12:1 or richer from the factory. Tthe ECM will turn on the check engine lamp in this mode.

A 10K ohm resistance in the diagnostic terminal to ground will invoke the factory End of Line Test Mode, or ALDL Mode. When the assembly line diagnostic mode is detected, the fuel logic will bypass the closed loop time criteria. The fuel logic will enter closed loop mode as soon as the coolant temperature and oxygen sensor thresholds are met. There will be no reset of the integrator function. The IAC will use the calibration memory table value corresponding to a battery voltage of 8 volts, bypass certain criteria for RPM closed loop enable, and bypass coolant restrictions for enabling IAC kick-down mode. The EST system will disable the Burst Knock logic and bypass the RPM and coolant temperature criteria for ESC retard enable. That will force the engine into a condition where spark knock should occur if the throttle is suddenly opened (Burst Knock). Additionally, if ALDL mode has been enabled longer than a PROM timer value, the timer will be removed from the spark advance calculation. The TCC logic will allow the TCC to be enabled sooner and without regard to the CTS input.

 

I would borrow a MAF from a good running car. That's what it was on mine!