Okay, I'm in need of help as I'm running out of troubleshooting steps here. This is a long writeup so thanks for sticking with me.
Car is an '87 325is (12/86 build date) with an M20 swapped in from a late '87 or early '88 car. I did not do the swap so only have the seller's info to go on. I have only had the car less than a month and it's been down the majority of that time so I don't have much of a baseline to know what's good and what isn't. Ran flawlessly on the test drive.
Prior to the exhaust work I did take the car out a handful of times and it always ran great. No misfires, pulled strongly to redline. The car has an aftermarket exhaust that had an exhaust leak. The car is lowered and the exhaust was routed poorly and it was scraping the ground over everything. So getting the exhaust fixed was top of my list.
Shortly after buying it I had a no crank situation. Discovered the car was missing the engine ground strap so I got a strap, installed it and car started like a champ. Took it to the local muffler shop and that's where this current mess all started.
Car has a long tube header that routes into a crossover which is where the O2 sensor is installed. Aft of the crossover there was a cat that had been dragged over the pavement so many times the bottom of it was full of holes. Aft of the cat was a bolt-on exhaust coupler that connected the piping to a Magnaflow muffler at the rear. I had the muffler guy replace the entire middle section with new pipe and route it better so it isn't hanging in harm's way. So now we have long tube header into crossover and then straight exhaust pipe to the Magnaflow muffler at the rear. No more cat.
On the drive home from the muffler shop I notice a misfire under load at higher RPM, maybe at 4k or above. It had definitely never done that in the short amount of time I had the car prior. I get home and a couple days later have some time to troubleshoot. Car started fine cold and no misfire while cold. Once warmed up it started missing again. At first only under load and at higher RPMs. The more I drove the worse it ran. I turned around to head home and it was running so poorly it stalled a couple blocks from home. Started it up, still running very rough but was able to limp home where it has been ever since.
Current situation:
- very rough running, at idle and with throttle input - makes no difference
- won't hold a steady RPM
- backfires
- MPG gauge spikes at every misfire - the needle shoots up to the max and then heads back toward 0 until the next misfire where it spikes again
- Temp gauge needle kind of wags a little with the misfires
Here's what I have done to date:
GENERAL:
- DME is a 153
- Installed new CPS. The original one had frayed wiring from misrouting so was suspect and needed to be replaced regardless.
- Installed new Coolant Temp Sensor. The original one seemed to test out okay but it's a cheap part so replaced it anyway.
- Ground connections:
AIR:
- Vacuum:
- AFM - flap moves freely.
- TPS:
FUEL:
- Injector wiring doesn't look in great shape. Black wire covers are age/heat hardened. #5 connector has a frayed positive wire but it gets a consistent 12V at key on.
- FPR - vacuum line is flexible with no cracks and no blockage.
- Fuel pump - Pulled back seat and opened access hatch. Listened for prime sound at key on but I don’t hear anything.
SPARK:
- Inspected distributor cap - clean and dry inside. Contacts look good. I did not pull the rotor but the topside that I could see looked in good shape.
- Spark plug wires - pliable and there are no cracks or damage. If I’m being picky #5 doesn’t attach to the spark plug lead as tightly as I’d like. Re-seated both spark plug ends and distributor cap ends.
- Coil - have not tested yet.
- Spark plugs - all 6 plugs in similar condition. Fouled with gas, smelled very gassy. Possibly some oily deposits as well. Autolite Double Platinum APP 64 plugs. Gap was set too wide according to Bentley. They were gapped to ~1.1mm. Bentley spec is 0.7mm. Re-gapped, cleaned and reinstalled. I have new plugs but have not yet installed them.
I make one change at a time and start the car after every change. Nothing has changed how it's running. When I installed the new crankcase breather hose it seemed like it stabilized the idle but as of this morning it is back to the same old rough running at idle and with throttle input.
I saw a thread where jlevie says that the MPG gauge spiking means the DME is not producing firing pulses for the injectors. I'm not sure how to validate this, any ideas?
Also, am I just chasing a ghost thinking this is connected to the exhaust work? I can't figure out how it could be causing these issues but it's a strong coincidence if it isn't connected.
If you've read all the way through I thank you. Any help on getting this sorted would be much appreciated.
Car is an '87 325is (12/86 build date) with an M20 swapped in from a late '87 or early '88 car. I did not do the swap so only have the seller's info to go on. I have only had the car less than a month and it's been down the majority of that time so I don't have much of a baseline to know what's good and what isn't. Ran flawlessly on the test drive.
Prior to the exhaust work I did take the car out a handful of times and it always ran great. No misfires, pulled strongly to redline. The car has an aftermarket exhaust that had an exhaust leak. The car is lowered and the exhaust was routed poorly and it was scraping the ground over everything. So getting the exhaust fixed was top of my list.
Shortly after buying it I had a no crank situation. Discovered the car was missing the engine ground strap so I got a strap, installed it and car started like a champ. Took it to the local muffler shop and that's where this current mess all started.
Car has a long tube header that routes into a crossover which is where the O2 sensor is installed. Aft of the crossover there was a cat that had been dragged over the pavement so many times the bottom of it was full of holes. Aft of the cat was a bolt-on exhaust coupler that connected the piping to a Magnaflow muffler at the rear. I had the muffler guy replace the entire middle section with new pipe and route it better so it isn't hanging in harm's way. So now we have long tube header into crossover and then straight exhaust pipe to the Magnaflow muffler at the rear. No more cat.
On the drive home from the muffler shop I notice a misfire under load at higher RPM, maybe at 4k or above. It had definitely never done that in the short amount of time I had the car prior. I get home and a couple days later have some time to troubleshoot. Car started fine cold and no misfire while cold. Once warmed up it started missing again. At first only under load and at higher RPMs. The more I drove the worse it ran. I turned around to head home and it was running so poorly it stalled a couple blocks from home. Started it up, still running very rough but was able to limp home where it has been ever since.
Current situation:
- very rough running, at idle and with throttle input - makes no difference
- won't hold a steady RPM
- backfires
- MPG gauge spikes at every misfire - the needle shoots up to the max and then heads back toward 0 until the next misfire where it spikes again
- Temp gauge needle kind of wags a little with the misfires
Here's what I have done to date:
GENERAL:
- DME is a 153
- Installed new CPS. The original one had frayed wiring from misrouting so was suspect and needed to be replaced regardless.
- Installed new Coolant Temp Sensor. The original one seemed to test out okay but it's a cheap part so replaced it anyway.
- Ground connections:
- new engine ground strap
- G103 - looks good and connections are tight
- G200 - looks good and connections are tight
- G300 - Kind of hard to see but connections look good and tight
- Battery ground connection is tight and clean on battery post and to body
- Electrical connections:- G103 - looks good and connections are tight
- G200 - looks good and connections are tight
- G300 - Kind of hard to see but connections look good and tight
- Battery ground connection is tight and clean on battery post and to body
- C101 - pulled rubber boots on both sides of connectors, wiring looks good and clean. Inside connectors the pins all look clean with no corrosion. Sprayed contact cleaner in connectors.
- Car has no C191 connector
- O2 sensor - I know this has no effect on cold operating but given the connection with the exhaust work it is in my mind. Looked under car and found the wiring from the sensor was hanging on the ground and torn. I found that there was a splice in the wiring with butt connectors and they were all torn up. I repaired wiring and reconnected. I have a new one to install but haven't done that yet. Could my drive where it ran fine cold and then got steadily worse have somehow fouled things up to the point where it won't run right now?- Car has no C191 connector
AIR:
- Vacuum:
- Installed new crankcase breather hose. Old one looked intact once I removed it.
- Line from charcoal canister to check valve under TB was open. Check valve itself has a broken off plastic connector where the vacuum line attached so I plugged the check valve connector and also plugged line off the charcoal canister.
- All 3 metal elbow fittings on TB were loose and would come out by hand. JB Welded fittings back into TB.
- TB rubber boot fitting is flexible and free of cracks.
- Valve cover had one very loose nut - tightened all of them.
- I know I need to do a smoke test but the car runs so poorly I'm not sure I could make it to a shop. I'm trying to get it stabilized enough that I can get this done.
- ICV - buzzes and vibrates with key on. Sprayed out with TB cleaner.- Line from charcoal canister to check valve under TB was open. Check valve itself has a broken off plastic connector where the vacuum line attached so I plugged the check valve connector and also plugged line off the charcoal canister.
- All 3 metal elbow fittings on TB were loose and would come out by hand. JB Welded fittings back into TB.
- TB rubber boot fitting is flexible and free of cracks.
- Valve cover had one very loose nut - tightened all of them.
- I know I need to do a smoke test but the car runs so poorly I'm not sure I could make it to a shop. I'm trying to get it stabilized enough that I can get this done.
- AFM - flap moves freely.
- TPS:
- Tested per Bentley - I get continuity at closed throttle - I do NOT get continuity at WOT. I have not adjusted it yet as the WOT issue should not be influencing current problem.
- Tested voltage at TPS connector. Per Bentley it should be at least 5V, I am only getting 4.68V. Not sure if this is a big enough difference to be of concern.
- Exhaust - considered possibility of plugged exhaust. Pulses from tailpipe are strong and when it backfires you can really feel the energy through the tailpipe. Pulled O2 sensor and left bung open thinking that might free it up if there was a restriction.- Tested voltage at TPS connector. Per Bentley it should be at least 5V, I am only getting 4.68V. Not sure if this is a big enough difference to be of concern.
FUEL:
- Injector wiring doesn't look in great shape. Black wire covers are age/heat hardened. #5 connector has a frayed positive wire but it gets a consistent 12V at key on.
- FPR - vacuum line is flexible with no cracks and no blockage.
- Fuel pump - Pulled back seat and opened access hatch. Listened for prime sound at key on but I don’t hear anything.
SPARK:
- Inspected distributor cap - clean and dry inside. Contacts look good. I did not pull the rotor but the topside that I could see looked in good shape.
- Spark plug wires - pliable and there are no cracks or damage. If I’m being picky #5 doesn’t attach to the spark plug lead as tightly as I’d like. Re-seated both spark plug ends and distributor cap ends.
- Coil - have not tested yet.
- Spark plugs - all 6 plugs in similar condition. Fouled with gas, smelled very gassy. Possibly some oily deposits as well. Autolite Double Platinum APP 64 plugs. Gap was set too wide according to Bentley. They were gapped to ~1.1mm. Bentley spec is 0.7mm. Re-gapped, cleaned and reinstalled. I have new plugs but have not yet installed them.
I make one change at a time and start the car after every change. Nothing has changed how it's running. When I installed the new crankcase breather hose it seemed like it stabilized the idle but as of this morning it is back to the same old rough running at idle and with throttle input.
I saw a thread where jlevie says that the MPG gauge spiking means the DME is not producing firing pulses for the injectors. I'm not sure how to validate this, any ideas?
Also, am I just chasing a ghost thinking this is connected to the exhaust work? I can't figure out how it could be causing these issues but it's a strong coincidence if it isn't connected.
If you've read all the way through I thank you. Any help on getting this sorted would be much appreciated.
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