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Problem first. As of the past week and a half, both my friend’s car and my own have been sputtering under load when it reached operating temperature (when it sputters badly, the low oil pressure light comes on). As of the past couple days, sometimes both vehicles will stall. Typically I can get to a safe spot to pull over if I have a smooth road and keep the RPMs under 1900. As of today, it’s getting harder and harder to get to a safe spot to pull over due to it stalling sooner. My friend switched from 5w-30 to 10w-40 and so far it has seemed to help him. Earlier today, I let my car idle with some Seafoam and then I changed the oil from 5w-30 to 10w-30 but my problem still persists. We both have new plugs (mine are NGK coppers with 7?? miles on them). I also have new wires and a fuel filter. I have checked a couple of my plugs and they seem to look great with no fouling (I plan to pull them all tomorrow). I have 38 psi at my rails on idle when cold starting. My wires have good resistance. My battery terminals are on snug. Oil and transmission fluid are at ideal levels (and checked a couple times a week to ensure good levels). I also poured some Seafoam in with the fuel in case the fuel was compromised.
So my plans for tomorrow are to pull all the plugs, check gap, and clean if necessary.
I was wondering if anyone else had this kind of problem or if they had any suggestions. My research has brought me to suspect the fuel pump (replaced about 22 months ago), Ignition module, Crankshaft Position sensor, or coil packs. I know a while back, my car threw a high/low voltage to fuel pump. I checked the relay and it was fine. I had the same voltage from the fuse/relay box (where the positive cable hooks up) all the way to the fuel pump which leads me to want to rule it out, but I won’t until I know for sure. Recently (before my recent plug and wire change), I had E3 plugs in and they had nearly all failed with 11,000 miles on them. I also do have a high output alternator rated at 220 amps (been on for 17 months) for my sound system (I also run an Optima red top battery).
Now for some info on my car:
1995 Pontiac Grand Prix SE w/ 3.1 SFI 60* V6 with 4T60-E
Current milage 174,???
Oil change at 174,??? (less than 30 miles on oil change so far)
Oil change at 173,???
Spark plugs, wires, and fuel filter at 173,???
Timing chain, coolant flush, and oil change (including all necessary gaskets) at 172,???
Complete upper gasket including head gaskets and all new bolts at 169,??? (Head gasket was cracked but only driven about 60 miles with little contamination) (compression test was done and I had 170-175 psi on all cylinder on a dry test.
Transmission flushed at 162,7???
Fuel pump, sending unit, filter, fuel pump relay, and strainer at 163,???
ALL fluids look, smell, and feel fine. I typically change the oil and filter every 2,200-2,800 miles.
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You should be running ac delco plugs. key on engine off
fuel pressure should be 40 psi. with the car running and
the fuel pressure gauge hooked up to the fuel rail. pull
the vacuum line off the fuel pressure regulator.see if fuel
pressure increases at least 10 psi. If not fpr is suspect
and should be replaced. For the oil light. Install a mechanical
gauge to see if you have oil pressure.So I ran a fuel pressure test again. Idle at 38 and with FPR line off it jumped to 45. To help rule out a faulty relay, I replaced it with an appropriate relay. Still same result for fuel pressure. But with the information you gave me, I will probably do some research tonight to see if anyone else had a problem with the fuel pressure regulator that had the same symptoms.
key on engine off pressure was at 40 psi. It holds pressure. I just rigged up my voltmeter so I can test the voltage near the fuel pump when it acts up. I highly doubt it’s a relay problem simply due to the fact that I switched it with a new relay. But I’m hoping maybe I’ll see some activity to help me find out if it’s a wiring issue from the rely.
So I just did a little more research. It seems that my car has a fuel pump and engine oil pressure switch. According to what I read, when the oil pressure sensor gives a bad signal, it affects the fuel pressure/delivery. It could also explain the low oil light. I will do a complete test on it (AC and ohm) tonight if I have time. Here’s hoping the resistance is out of spec for a cheap and easy fix. I’ll let you know the readings from it.
So hooked it up to my friend’s Modis. Fuel pump was running fine. When looking at my code history, it said that my EGR solenoid number 3 had a problem. I unplugged my EGR wires and so far it has ran fine on the roads it broke down on yesterday. Ill give it a few days before saying that fixed it. But if I don’t post anything, then chances are it fixed it. Here’s hoping.
And apparently GM vehicles have their oil pressure sensor control a switch for fuel . Probably as safety feature to prevent total engine fail in case of oil pressure loss.
If it was the EGR, I imagine the computer saw it and caused the fuel or spark to shut off to prevent running massively lean or rich. Due to that, I imagine oil pressure was dropping as well to help stop the vehicle to prevent damaging the engine. I am one of the lucky people with MGM’s test dummies. OBD2 computer with an OBD1 port (which is why I used the Modis).
GM, not MGM. Gotta love smart phones.
I have driven it for another hour since, no problems yet.
However, my friend’s car is still acting up. He has a 1991 Honda Civic Si. Same problems I had. However, he doesn’t have an EGR and does have OBD0. It does have the ZC motor in it (JDM version of the D16A6 that came with it stock). He wanted to replace his oil pressure sensor. So we did. Still died on him. He has been experiencing high idle as of late. I am going to run to O’Reilly’s really quick to grab some carb spray. If it smooths out permanently or for a few minutes, I plan to check the IAC. If it smooths out for moment, we will test fuel pressure (it does have a newish fuel filter) and possibly replace the intake manifold gasket just in case (reason is that it only wants to stall on lower RPMs). It likes to start idling at 1500 and eventually drops to 1150 and then likes to stall. We have noticed what seems to be like an oil and gas mix out of the tailpipe and fuel smell in the oil. We have reason to suspect the regulator is going out. No fuel in the hose on the top of it. One of our main problems is the fact that I have no idea where to hook up the fuel pressure tester. We cannot find a single spot to hook my tester up to in the engine bay. Anyone know of a place where to hook the fuel pressure tester up to?
You need a special banjo fitting. here is a quick check method.
We know we have fuel, but I want to make sure we have enough fuel.
So I sprayed some Carb spray down the intake. Kept adding a little Carb spray during idle. After a while it was idling at 950-1000 rpm fairly well. So tonight we are going to take off the IAC and MAP and clean them well. We are not ruling anything out. My friend is concerned his head gasket is blown so I’m probably going to change it and check all the valve clearances while I’m at it if he really thinks it’s the head gasket.
Meanwhile, my Grand Prix is driving around amazingly still. I should mention I live in the mountains and our roads are barely in decent condition. So it’s easy to put a load on any vehicle.
We cleaned the IAC and MAP. It runs and idles really well. We have yet to drive it. We have more reason to believe the head gasket is blown. Plus there is a little valve noise. So if the head gasket is blown or cracked, we are going to do a full head gasket kit, head bolts (better safe than sorry), valve adjustment, and new timing belt (depending on it’s inspection).
My Grand Prix is still running very well. Got some power back. Spinning and chirping tires all day again. Also, it seems that I have had better gas mileage than I ever did before. Before I’d get about 200-250 a tank in town if I baby it. I have driven about 50 miles and only used 3/16th of a tank at best. Meaning I’m getting about 266 miles a tank so far with fairly hard driving (again, I live in the mountains).
In regards to my friend’s civic, he finally listened to my first suggestion (which was to check the distributor and rotor). Upon removing the cover, a fairly large crack was discovered on the distributor. He is in the process of finding a used one (in good conditions ) to keep cost down in case it wasn’t the culprit.
As of 2 days ago, under load my car backfired once or twice. Yesterday, backfired in the same place with the same load. Today, it was acting up again. So I talked to my friends boss (who owns a successful shop here). He suggested I loosen the exhaust up as it my be the cat plugging up. I will do that tomorrow night most likely and test it. It is possible that it is the cat. I may have failed to mention that I drilled a 1″+ diameter hole in my cat when I did the head gasket to help it run at the time. I do believe I plugged up the hole shortly before problems arose. I don’t have faith that it’s the cat simply because when I drop it into neutral, it will rev just fine (even when its acting up). I’m starting to think it might be my transmission line pressure. Gonna do some research behind line pressure symptoms.
Well it’s been a week since I last updated. I reopened the hole I had patched in my catalytic converter, didn’t help really. After some looking around transmission issues that could cause this, I found that the TCC solenoid could possibly cause my problems currently. I unplugged my TCC solenoid and drove around for a bit. Not a single problem. Reconnected it and it ran fine for a while (happened for one very small split second and that was that). So I went to find out the cost of the TCC solenoid and it appears to also be the shift solenoid (maybe most TCC solenoids are, I don’t know transmissions very well). It explains my issue with not always wanting to shift into fourth gear on the highway. This upcoming paycheck I’ll replace it along with my filter and gaskets. Only about $55 so it’s not bad if it don’t work. Also, I have read that the TCC solenoid is horribly bad at failing on the 4T60E transmissions (which is what I have). I’ll keep you updated.
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