Here's a TLDR if you don't feel like reading everything below.
I think I have a misfire issue that only happens intermittently, usually on rainy days, and can go away for days/weeks at a time. The motor won't rev past 2-2.5k rpm under load, but revs freely in neutral. At idle, the car sounds like a cammed LS when idling, exhaust smells like fuel, and the engine shakes. If I keep the throttle pinned, it will sputter and sometimes climb up in rpms until it breaks through and runs normally. It goes away once warmed up or after 1-2 minutes if the holding the throttle doesn't work. Fuel pressure and injectors seem to be fine. Spark plugs seem okay. I definitely have a head gasket leak (oil) and very low compression in cylinder 6, which I think may be causing the issue.
Video of the issue
The long story
I've been trying to chase down a misfire I've been getting from time to time for the last year and I think I may be closing in on the issue.
A little background. I bought a 1986 325es with about 145k miles on the clock a little over two years ago. I did two major services on the car and began running into a misfire issue after the second service.
When I bought the car, I did all the typical maintenance. Oil change, fuel filter, camshaft seal, water pump, timing belt, spark plugs, ignition components and wires. I got the car re-assembled and drove it around without any issues.
The second round of maintenance, I installed power steering, I replaced the intake manifold with a powder coated one, replaced the starter, replaced the fuel injectors with refurbs, and did a valve adjustment, along with a bunch of smaller non-critical items. It was here where I ran into an issue getting the car to start.
After reassembly, the car wouldn't start. It turns out I forgot to reconnect the O2 sensor wire back. I got the car started, but it was running incredibly rough. After some quick diagnosis, it turns out four of my fuel injectors were stuck and not providing fuel to the cylinder. I had them sent back to where I bought them from to get them refurbed again and eventually got them back in the car. Viola! The car ran fine. At least I thought it did.
After a few days of driving the car, I ran into a problem where I would get into second gear and the car wouldn't want to rev past 2,000 rpm. It would hit what seemed like a false rev limit and stayed pinned at that rpm. If I shifted into third, the car would accelerate some more and than stop at maybe 1,800 rpm. The higher gear I went into, the lower the rev limit dropped. If I shifted into neutral, the car could rev to red line with no load. When I let it drop to idle, it would idle at like 500-600 rpm and run roughly, almost sounding like a cammed LS with that glugging/gurgling sound.
If I stomped on the accelerator and held it, it would try and rev past the limit and slowly climb up in speed and the issue would go away. Usually this would happen for a minute or two at a time. Once the engine was warmed up and it stopped with the misfires the first time, it wouldn't come back as long as the engine didn't cool and sit for a few days.
After experiencing the issue several times, the common denominator I found was that it would typically occur during or after a rain fall. I thought maybe there was an issue with moisture on some sensor or something.
Everywhere I read said it's probably a CPS issue, so I replaced that. The car ran fine for a while and I thought that was it. Nope. Eventually the same issue came back.
I thought maybe it's a vacuum leak causing the problem. I had the car smoke tested and it turns out I had a major leak at the oil return tube from it not seating right (I guess when I was taking the manifold on and off trying to figure out the no-start the first time). The guy was shocked my car was even running. I just recently tore everything apart and got that fixed. There is still a tiny, tiny leak at the throttle body bearing, but I highly doubt that it's causing the issue if the car ran with the massive leak at the oil return tube.
After fixing the vacuum leak, I got the car back together. It felt so much more responsive and the throttle felt snappier. I wasn't getting that misfiring issue and I was happy. I thought I fixed the problem. Nope! It came back again after a few days. This time it seems to be appearing more often.
I always thought it may be something with the fuel injectors after having four of them stuck, but they seem to be ticking just fine and the fuel pressure in the system is to spec.
I finally decided to take out the spark plugs and inspect them. They have some oil on the threads. Cylinder 1 actually had a decent amount of oil on it.
I ran a compression test and it looks like cylinders 3 and 6 may have a problem. I know cylinder 6 definitely has low compression. Unfortunately, the gauge I used is some garbage Amazon one, so the readings were actually showing 180 psi for the good cylinders. I tested it with a compressor and think it's out of whack about 30 psi. I'm going to recheck with a higher quality compression test kit.
1 - 150
2- 144
3 - 130
4 - 148
5 - 148
6 - 60-90
I also have a pretty good oil leak from the head at cylinder 6 which I think may be more than just your typical M20 weeping gasket. There is some leaking at the front of the motor as well. I'm assuming this is what's causing my misfiring, rough running, false rev limit issue. I don't think it's leaking coolant, because my coolant levels have stayed the same the past two years.
What is the next step here? I was going to retest the compression and then check the valves to make sure they are still within spec. I'm assuming I want to do a leak down test to try and narrow down exactly is going on?
I'm planning on doing a head gasket replacement. My plans for this motor are to eventually turbo it, but I think I may save that for next year to try and get the car back up and running before spring instead of rushing a turbo build.
Are there any other items I can replace, upgrade while doing a head gasket replacement?
I think I have a misfire issue that only happens intermittently, usually on rainy days, and can go away for days/weeks at a time. The motor won't rev past 2-2.5k rpm under load, but revs freely in neutral. At idle, the car sounds like a cammed LS when idling, exhaust smells like fuel, and the engine shakes. If I keep the throttle pinned, it will sputter and sometimes climb up in rpms until it breaks through and runs normally. It goes away once warmed up or after 1-2 minutes if the holding the throttle doesn't work. Fuel pressure and injectors seem to be fine. Spark plugs seem okay. I definitely have a head gasket leak (oil) and very low compression in cylinder 6, which I think may be causing the issue.
Video of the issue
The long story
I've been trying to chase down a misfire I've been getting from time to time for the last year and I think I may be closing in on the issue.
A little background. I bought a 1986 325es with about 145k miles on the clock a little over two years ago. I did two major services on the car and began running into a misfire issue after the second service.
When I bought the car, I did all the typical maintenance. Oil change, fuel filter, camshaft seal, water pump, timing belt, spark plugs, ignition components and wires. I got the car re-assembled and drove it around without any issues.
The second round of maintenance, I installed power steering, I replaced the intake manifold with a powder coated one, replaced the starter, replaced the fuel injectors with refurbs, and did a valve adjustment, along with a bunch of smaller non-critical items. It was here where I ran into an issue getting the car to start.
After reassembly, the car wouldn't start. It turns out I forgot to reconnect the O2 sensor wire back. I got the car started, but it was running incredibly rough. After some quick diagnosis, it turns out four of my fuel injectors were stuck and not providing fuel to the cylinder. I had them sent back to where I bought them from to get them refurbed again and eventually got them back in the car. Viola! The car ran fine. At least I thought it did.
After a few days of driving the car, I ran into a problem where I would get into second gear and the car wouldn't want to rev past 2,000 rpm. It would hit what seemed like a false rev limit and stayed pinned at that rpm. If I shifted into third, the car would accelerate some more and than stop at maybe 1,800 rpm. The higher gear I went into, the lower the rev limit dropped. If I shifted into neutral, the car could rev to red line with no load. When I let it drop to idle, it would idle at like 500-600 rpm and run roughly, almost sounding like a cammed LS with that glugging/gurgling sound.
If I stomped on the accelerator and held it, it would try and rev past the limit and slowly climb up in speed and the issue would go away. Usually this would happen for a minute or two at a time. Once the engine was warmed up and it stopped with the misfires the first time, it wouldn't come back as long as the engine didn't cool and sit for a few days.
After experiencing the issue several times, the common denominator I found was that it would typically occur during or after a rain fall. I thought maybe there was an issue with moisture on some sensor or something.
Everywhere I read said it's probably a CPS issue, so I replaced that. The car ran fine for a while and I thought that was it. Nope. Eventually the same issue came back.
I thought maybe it's a vacuum leak causing the problem. I had the car smoke tested and it turns out I had a major leak at the oil return tube from it not seating right (I guess when I was taking the manifold on and off trying to figure out the no-start the first time). The guy was shocked my car was even running. I just recently tore everything apart and got that fixed. There is still a tiny, tiny leak at the throttle body bearing, but I highly doubt that it's causing the issue if the car ran with the massive leak at the oil return tube.
After fixing the vacuum leak, I got the car back together. It felt so much more responsive and the throttle felt snappier. I wasn't getting that misfiring issue and I was happy. I thought I fixed the problem. Nope! It came back again after a few days. This time it seems to be appearing more often.
I always thought it may be something with the fuel injectors after having four of them stuck, but they seem to be ticking just fine and the fuel pressure in the system is to spec.
I finally decided to take out the spark plugs and inspect them. They have some oil on the threads. Cylinder 1 actually had a decent amount of oil on it.
I ran a compression test and it looks like cylinders 3 and 6 may have a problem. I know cylinder 6 definitely has low compression. Unfortunately, the gauge I used is some garbage Amazon one, so the readings were actually showing 180 psi for the good cylinders. I tested it with a compressor and think it's out of whack about 30 psi. I'm going to recheck with a higher quality compression test kit.
1 - 150
2- 144
3 - 130
4 - 148
5 - 148
6 - 60-90
I also have a pretty good oil leak from the head at cylinder 6 which I think may be more than just your typical M20 weeping gasket. There is some leaking at the front of the motor as well. I'm assuming this is what's causing my misfiring, rough running, false rev limit issue. I don't think it's leaking coolant, because my coolant levels have stayed the same the past two years.
What is the next step here? I was going to retest the compression and then check the valves to make sure they are still within spec. I'm assuming I want to do a leak down test to try and narrow down exactly is going on?
I'm planning on doing a head gasket replacement. My plans for this motor are to eventually turbo it, but I think I may save that for next year to try and get the car back up and running before spring instead of rushing a turbo build.
Are there any other items I can replace, upgrade while doing a head gasket replacement?
Comment