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Does sound like an electrical problem. First thing I would check is how clean is the GROUND signal on your car/chassis? If your GROUND is noisy, that problem gets worse when the car is hot (impedance increases with temperature). Ground noise will decrease the +12 voltage used for the MAF readings, DME's ability to drive the injectors, fuel pump's ability to maintain flow etc..
I will check ground signal and FPR vacuum lines + test fuel pressure at the rail and share results ASAP. Reading tons currently about the difference in fuel cut vs boost cut vs spark blowout. I've pressurized the system to complete a boost leak test with no leaks found recently.
- What type of boost controller / wastegate system are you running? Manual or electric?
- You say the AFR bounces between 13 and 17. This a wideband setup, right? Interesting that it swings like that...seems like it's behaving more like a narrow band sensor trying to manage the mixture.
- I concur with Tom it would be super helpful to get the AFR reading while the problem is occurring.
- I also concur with checking the grounds...seems like lots of odd problems have been solved by this.
- Was the engine warm or cold when you did the intake pressure test? Warm would be best if you can manage it...
Curious one for sure. Going to have to be methodical to chase this one out.
LR manual boost controller / Tail 38 Wastegate.
AEM Wideband 02 yes
Any insight on checking the grounds? (immediately googling this)
Engine was cold for the pressure test. I will add to the laundry list to check on a hot engine.
Plugs are pretty rich/coated when I pulled them. I'm running NGK BPR7ES as one range colder and gapped them down to .028. Only running 15psi max but with the bigger turbo it moves a lot more air than stock - thus the reason for the colder plug. Maybe overkill? Maybe not getting the plugs up to the "natural burn off/self cleaning range" around town and they are fouling? I'll post a pic when I check again. Wires are grey BERU OE wires - I don't see any splitting and they seat nicely. I've ordered a new BOSCH cap and rotor and will certainly look at wires as a next step.
Well things have changed a bit - went for a drive last night to continue to dig into this and symptoms/issues appeared immediately upon leaving the garage (NOT a restart/hot start issue anymore). This changes the diagnosing process a bit. Car had sat in the garage since Thurs, fired right up and idle was lumpy. Giving it a little throttle produced a burping/stuttering. Drivable but the moment I roll onto the throttle it cuts out and backfires. Took her out on the highway and after a few burps she will still pull like a freight train - boost gauge pegs at 15psi and AFRs were 11:2 /11:5 as best I could tell at WOT. Still need to log properly and take a video of gauges as alternative.
Apologies for mega-image. When going over grounding points as suggested - I have realized this driver side connector and it's fragile housing is broken. Two of the wires are cut (looks like clean through) while the brown wire still connected to the ground. Issue here? Besides being ugly - I need to trace the harness back and see what's not connected.
That’s your brake pad sensor connector, it’s not your issue. Have you had your car tuned to your setup? If so maybe your MAF/AFM or TPS may be going south. Also a temp sensor sending bad info to the computer could creat major issues. If the engine thinks it’s cold it will dump more fuel. Change your plug wires also if they are stock or old.
This just keeps getting better and better. If anything I'm learning lots. Went to test fuel pressure on the rail today - borrowed a tester from local auto parts store - noticed it had some metric adapters and when I got home of course realized it did NOT have a 12 x 1.5 adapter. So that is on hold til I source/make an adapter. When going over everything I realized looking at the serial number and script on the FPR that it's in fact a 2.5 BAR OE FPR not the 3.0 I thought the PO had installed. Still will test pressure at the rail when I can but...
All these years and I didn't learn what those things on either side of the engine were till now!! My buddy's '86 doesn't have them; I always thought they were airbag related.
As for the running issue.. does sound like TPS symptoms I've read elsewhere....
All these years and I didn't learn what those things on either side of the engine were till now!! My buddy's '86 doesn't have them; I always thought they were airbag related.
As for the running issue.. does sound like TPS symptoms I've read elsewhere....
The pre 87 models don’t have the brake pad sensor connector in that location, they have a small round style connector for the brake pad sensors mounted on the strut itself nor are they close to the same connectors from pre 87 and 87 on. The 87 onward ABS optioned cars have a huge round female connector in the same location as yours and on the car harness side with three socket locations, one for the brake pad sensor, the other for the ABS sensor and the last is usually plugged and has no terminals in it and what I’m making up was for future NASA use for when the car’s fast enought to catch flight. To help trim in the control surfaces.
Deleting all the brake pad wear sensors today in fact. Trying to clean up any loose and suspect looking wiring throughout the car as I go through it. Glad I know now exactly what I'm dealing with! Keeping this thread on track though - I did an EVAP system delete yesterday to eliminate a huge number of potential vacuum leaks and connections. I also chatted with Dave at LR and immediately ordered new 3.0 Bar FPR. I also (after reviewing above comments about the TPS again) was going over things and noted my TPS is only held on currently by ONE SCREW and the top plastic cover had nearly blown off. I had tested the TPS through the DME procedure and it tested fine a few weeks ago but this seems problematic. I immediately ordered a throttle body rebuild kit and new mounting screws as well.
07-20-2018, 11:08 AM
