My 90 L98 was running after completion of the following:

Stage III Heads/Comp Cam
Comp Cams Timing Chain
52mm TB
24# Fuel Injectors
LT Headers
Edelbrock Intake/Runners
Ported OEM Plenum
1.6 RR's
Walbro Fuel Pump
Random Tech Cat
Flowmaster II's
Chip Tune By Mail (just to get started)

The car was run for approximately 100 miles after the mods were installed. From the start it seemed to have a "hitch" at idle. The best way to describe it was it felt like an ignition miss. At around 1500 rpm the miss was gone. This led me to believe it was not an ignition problem. Today it started when cold but got progressively harder to start when warm. It would start but did not want to idle and when it would die there was an odor. It smelled like the old family car did when I was a kid and it would not stop running even though the key was turned off. We called it "dieseling" and the smell was like nothing else so it was easily recognizable. I checked the timing one more time -- 8 deg BTDC with the brown wire disconnected. I decided to take it for a drive and while I was going about 25 mph it just died. I was not accelerating just idling in the neighborhood. i checked the timing while cranking and it was sitting where I set it and #1 cylinder was getting spark. I did not have time to put my fuel pressure gage on it but the scanner showed the fuel pump was getting 13.8 volts.

Earlier when I checked the fuel pressure it was around 42 psi at idle but would fall to around 38 psi when I applied some throttle. I am just mentioning this for information purposes. I don't know if it means anything or not but I think the pressure is a little low.

Back to the problem. After the engine died, it would crank but acted as though it was not getting any fuel or spark. As I said earlier the timing light showed the #1 cylinder was getting spark.

I am writing this in hopes I get some ideas before I start troubleshooting tomorrow. I have an AutoXray Scanner and I have scanned the car since the mods were completed but as I am new to scanning I really can't say I completely understand the relationship of the perimeters I scanned.

I was planning on taking the car on a trip this next week so this has little problem has really put a damper on my plans so any help would be appreciated. Maybe there is still time to salvage my trip.

Thanks,

90Indy

 

Sounds like an ignition module failure

 

same thing happened in my old Iroc. it was the ignition control module. not sure about the l98, but in the 305tpi, it took 10min to fix once i figured out what it was.
good luck.




randy

 

If it is the ignition module, why would I continue to have a spark (as indicated by the timing light)? Also, where is the module located?

In any case I will look into it tonight.

90Indy

 

I would start with the basics...make sure you have spark on all the wires. Then make sure you have fuel pressure. Check your fuses for the injectors. There are two of them in there. I have seen/heard of them blowing out and people loosing injectors after mods. Not sure why, but they did.

If all that checks out, then you have some more digging to do.

Good luck.

 

Have you raised the idle? cam specs?
I bet you have tons of unwanted fuel at idle.
For this, you need the chip re-done.
-Beppe-

 

Checking the fuel injector fuses sound like a good idea. Where are they located? I checked all of the fuses in the box on the passenger's side and all were good.

90Indy

 

That is where they are at.

 

located inside distributer. not sure why you would still have spark. i know that in my roc, i was driving down the road and the thing just quit. all accessories still worked, it just wouldnt do anything when u turned the key. turned out to be ignition control module. your issue could very well be something different, so good luck finding and fixing it. sorry im not more help





randy

 

Here is what I did tonight.

Hung a fuel pressure gage. 42 psi while cranking. Sat for over 20 minutes and it still read over 40 psi.

Checked every plug wire using my inductive timing light and all showed to have spark.

Removed the ignition module cover and checked the coil wires and connections to the distributor. All looked good.

Disconnected the EST wire and checked the timing while cranking. The timing was steady at 8 deg BTDC. I saw nothing unusual.

Scanned for codes and the car threw a 42. This code deals with the EST. It may have been thrown while I was cranking with the EST disconnected. My AutoXray would not clear the code so I am trying to find out how to clear the code.

I even tried to start it using starting fluid sprayed into the TB but the engine did not even spit or sputter. It cranked over just fine but acted as though it was getting no spark or fuel.

At this point I don't know what to do next. I am hoping against hope that someone will respond with their solution to a similar problem. I really don't want to throw in the towel and haul it down to the dealer. Give me some ideas. Crazy or not. All comments more than welcome.

90Indy

 

Was the cam degreed with a degree wheel, pointer and piston stop?

 

If you sprayed starting fluid in there and it did nothing, you don't have spark. Even if the cam were off or the distributor was off it should have done something with ether being sprayed in there. The timing light may be flashing when hooked to the wires but you may not have enough juice to actually jump the spark plug gaps.
Get a spare plug and hook it to a plug wire, crank the engine while holding the plug against a good ground (engine block, exhaust manifold etc). You should get a nice hot looking spark on the plug tip...if not, I'd replace the module.

 

Check wiring IAC 4 wire weather pack at dist,plug for Maf,TPS .054.
Check carbon in center of dist cap.
A wire sounds like it went to ground.

 

Morley, the possibility of insufficient spark is the train of thought I tend to agree with at this point. It may be that the timing light way of checking for spark is giving me a false sense of security. The light may not require anywhere near the amount of electrical energy the spark plug does in order to jump the gap. I would think if I had one or two bad wires/plugs the engine would at least act as though it wanted to start. The ignition module has less than 1500 miles on it but I will locate the OEM module and install it. The car was running at one point so I don't think it is a mechanical issue, jumped time, cam installed incorrectly etc., at least not yet.

Thanks for the input,

90Indy

 

same problem with mine, accel module crapped out after 3k miles, replaced with a stocker and it ran like a champ, accel on backorder from summit will have to wait till mid august!

 

If you suspect week spark try a spark tester. They are about $5 at the local parts tsore and normaly have a chart on the back of the package that tells you what to set it to for your system. I had a similar problem when my opti died and when I checked with the tool at the specified gap it was DOA. It would show a week spark with the plug but wouldn't jup the gap when the tool was on there. Not a bad tool to have in the tool box and it is fairly cheap.

 

FD2BLK, great idea. I think I can find $5.00 in the couch tonight. If not I know where the kids piggy banks are. From all accounts it sounds like I put too much reliance on the timing light as the go/no go meter when determining spark energy. I will post my findings tonight if I get a chance to work on it.

Thanks to all,

90Indy

 

Here is what I have done and still no spark:

Replaced the distributor cap/rotor
Replaced the ignition module
Checked all fuses in the main fuse box (passenger side)

I ran several voltage checks according to the GM Service Manual and all checked good. The car through a code 42 and I tried to clear it by disconnecting the battery (left it disconnected all night) and when I scanned the car this morning the code still showed up. I did not try to crank the car before or during the this scan.

I know there is an oil pressure switch that sends a signal to the ECM when the oil pressure gets to 4 psi during start-up. Is it possible this signal is not being sent and therefore no spark or does this signal just tell the ECM to run the fuel pump and energize the injectors?

Remember this car was running and died while I was doing about 20 mph in the neighborhood. I have run out of things to check and am considering taking it to the dealer but I REALLY don't want those guys tinkering with my car. I also hate to admit defeat. I am appealing one last time for any pointers. I will even accept collect calls if you think you might have an idea that is better explained over the phone. Just pm me and I will give you my number.

Desparate in Dallas,

90Indy

 

Did you verify 12 volts at the distributor to the coil? Do you have a spare coil to try?

 

Did you have a look at the spark plugs ? Wet or dry ? White or black ?
I'm Not a good troubleshooter but this info may help.