'91 olds 98 won't start

[ythraccm]

The car is a '91 Olds 98 Regency Elite with 3.8 liter v6 with 117000 miles, Auto transmission

After having a radiator split and overheating, it was towed to a radiator repair shop to have radiator replaced. Upon picking up the car from shop the car would not start. All it does is backfire occasionally thru the intake and kick back. the compression reads 145 -155 on all cylinders except #4 which is 110psi. The plugs were gas soaked upon removal and #3 plug had a carbon bridge across the gap. But plugs look fairly new. Cleaned and dried plugs and cranked engine over and let cylinders dry overnight. Removed all fuel injector leads and tried starting engine by spraying starting fluid thru the intake.
The engine exhibited the same response as before backfiring and blowing off some of the vacuum hoses.
I have checked the timing by removing valve cover and feeling out #1 cylinder top dead center and verifying that both valves were closed and marking a timing mark on flywheel that could be observable with a timing light using the engine mounting bracket just above flywheel. The ignition timing seems to be about 10-15 degrees before TDC as marked while cranking. the valves seem to be opening and closing at the proper time meaning that the exhaust valve opens close to bottom dead center and closes while intake valves open close to top dead center on 3rd stroke going down, etc. The spark seems to be possibly a little weak but does jump the gap. I will check the coil pack resistance and see if it reads 10-15 ohms primary and 3k-4.5k ohms on secondary as found on another thread.
I'm doing this for an 80 year old man who hasn't much money would appreciate any help.
Thanks in advance.

[maxwedge]

Welcome to AF. Disconnect the maf see what happens, if you have a scanner check for cranking rpms, if possible get the icm tested maybe at AZ, or Napa.

[ythraccm]

Thanks for the reply,
Is ICM the ignition coil module?
New developments. Seems as though I got it working now.
The coil packs checked out OK with resistance checking. Got 1 ohm on primary and 12000 ohms on secondary. all within a 100 ohms or so on all 3 coils. Did find that the signal wire for one of the coils was cut into by the signal terminal of the center coil causing 2 coils to fire simultaneously. Corrected that problem but with no change in results.
I went through and checked all the spark plug wires and recleaned and dried plugs. Found a cracked plug on #2 and an open ignition wire on #4. Changed all the plugs and wires on suggestion of a local mechanic/friend.
The car woould now start, idle rough for a few seconds and quit. Pulled plug on #1 and it was sooted up. Checked fuel pressure regulator and it was running at about 49 psi. Specs say should be 40-47 max. Checked diagpragm on regulator and pulled full vacuum with no leakage. Fuel pressure dropped to about 30 psi Cranked engine and it idled rough at 30 psi fuel press. but it ran.
Obtained scanner and it said no codes OK to drive. Cranked engine, still a very rough idle but continued to run. No new codes genereated. Service engine light still on no check engine light, coolant hot indicator still lit.
Raced engine up and it smoothed out but idled badly and would stall if I letoff too quick. I played with A/C controls and all of a sudden, the indicator lights cleared and the engine smoothed out. I Sprayed out the MAF with carb cleaner wwhile racing engine and things continued to improve.
Now it runs pretty darn good. Still not sure what happened. But I am sure glad I don't own a GM.

[ythraccm]

This is a follow up.
After letting the car sit overnight, found the problem had returned. It was hard starting and the hot indicator and service engine light returned. Upon starting however, after revving up the engine, the lights would clear and engine would run smooth again. The same problem reoccurs evrytime it is shut off. Kind of like the alternator has to start putting out before it smooths out. While it is idling rough before I rev it up, the indicaor lights kind of flicker.
So my guess is the PCM is still having a problem. Cleaned off the battery cables and checked the pins at the connectors of both power leads for the PCM and I am getting 12 volts. the ground wires do seem to have a high resistance of around 18 ohms however.
If anyone has any other Ideas would appreciate hearing about them.
Thanks

[maxwedge]

18 ohms is too high, also check the alternator out put. Watch the engine sensor grounds .

[ythraccm]

I fixed the high resistance ground problem. Bad crimp on engine ground to chassis ground jumper. Still same result. Went on ahead and replaced ecm but used same eprom, (don't know anyone that checks eproms.) Still have same problem.
I did find out in owners manual that the service engine light will remain on until engine runs, I don't know if the Hot light should also stay lit until the engine is running, but they seem to be linked together on the same bulb test circuit.
So as of now the longer the vehicle sits up the harder to start. If I crank it up immediately after shutting down it starts fine, but idle is only slightly erratic.
Is it possible the intake manifold may have cracked if it overheated?
Also checked the alternator and it is fine around 14.7 volts. I pulled the excitation wires off the alternator and the starting results were the same.
I haven't yet tested the ICM. I presume it is working fine since the engine runs good above idle.

[maxwedge]

Don't discount the icm here, you can get it tested at AZ, but those tests can be inaccurate.

[ythraccm]

I will get that tested this evening and let you know.

Called autozone. They cannot test the type of ignition module, Napa doesn't test at all here.

[tyflesh]

had the same problem with my 91/98 i didnt go through all the steps you did because,when i replaced the coil pack a few years back it posed the sam problem, so i took the coil pack and the ignition mudule off and took it to autozone and they did check them both, and the ignition module was bad, so i dont know why they told you they dont check them when they do, maybe that person didnt know how or didnt know which test to use but they have a book with the directions in it on how to and what tester to us.....

[ythraccm]

I don't know why he told me that, did yours have the type 1 ignition coil pack on it? I wouldn't think it would make any difference but maybe it does.
In the meantime I'm rechecking for vacuum leaks and found a couple. Pulled and cleaned throttle body and IACS, PCV valve and cleaned both. Have not found an EGR valve anywhere on this engine. haynes says it has one and so does alldata.

[ythraccm]

Maybe I should start a new post as the car will now start but is hard to start when cold.
I had the ICM module checked at autozone. It was as I figured good.
All vacuum lines were checked and fixed all leaks including a vacuum tank seam leak.

It idles rough for a few minutes until it warms up a bit.
If I try to use the A/C the the engine loads up and tries to stall out then picks up. But the A/C compressor keeps cycling on and off probably due to the reduced idle speed. After turning the A/C off the engine continues to seem to try to stall out and recovers and cycles like that until it warms up. Once it warms up the problems go away and it runs smooth.
I wonder if the CALPAK or mempak in the eprom could have gone bad somehow?

Thanks for the help and ideas.

[maxwedge]

Get a scanner on it and look at the temp sensor readings should be outside air temp when cold and warm up with the engine, also look for lazy o2 activity. Look for raw fuel in the vacuum hose to the fuel pressure reg. also.

[ythraccm]

No fuel in fuel regulator vacuum hose.
I will check again with scanner but I believe that they were good at last check.

The air and coolant temp sensors were checked with DVM at room temp of 80 degrees. the ohmic values at 80 degrees were close to alldata specs as close as I could determine since they aren't linear, but it fell within a 11 to 18 degree range depending on which chart I used. And they do change resistance properly when heated or cooled.

I applied a resistance box to the CTS leads and preset the values to ohm values equivalent to around ambient when engine was cold.
If it was a CTS problem this should have corrected it. I set it both upward and downwards on the resistance. As I increased the resistance (fuel richer in response to lower engine temp.) the engine would speed up, but the engine hunting would continue until the engine actually warmed up. But indications seem to indicate now that the engine is running too lean.
Even racing the engine above idle around 1200 rpms holding throttle steady the engine continued to hunt(try to stall and come back to set speed) while cold. Almost like the timing was shifting (which I will now check now that I thought of it) or something was opening & closing in the throttle.
Also noticed that the harmonic balancer had about a .010 run out just eyeballing it. I was told that it could affect it. Is that true and wouldn't it hold true even when the engine has warmed up?

[maxwedge]

.010 runout means nada here unless the outer ring is seperating from the damper portion of the inner hub. common occurence on these engines.. Are you or have you monitored the fp during this event, also have you tried the maf disconnect?

[ythraccm]

I haven't monitored the fuel pressure while starting or running yet but I will do that. Only a engine off key on test which as mentioned before gives 49 psi at the test port.

As far as the mass air flow sensor, I have pulled the connector and it doesn't seem to affect the starting or running either hot or cold. The service engine light comes on while it is disconnected and when reconnected the engine stalls out and has to be restarted.
As far as the damper is concerned I tried to rock the pulley and it seems not to move relative to the hub which if it was coming loose I should be able to do?