Today I share with you, a lesson in the KISS principle.
I know, I’ve been a bit absent on here recently, but some things in life have come up and I havent really felt like or been able doing much on the cars. The other issue was that I wasn’t even sure if I would turn this “experience” into a full post, but I feel I need to share, both the highs and the lows as it may help someone in the future.
So last post I changed the fuel pump and filter out because the car decided to have an intermittent hesitation when coming on the throttle. I found some metal flakes in the filter, so the pump wasn’t happy anyway, but as it turns out I may not have NEEDED to change the pump at this point.
I thought the hesitation was finally sorted with that, but no, it wasn’t. The issue had been randomly popping back, until it finally progressed to the point where the car would try to stall when taking off from an intersection. It would just fall flat on its face when you opened the throttle. It would stutter, backfire, and then off you would go. Even the transition from off to on throttle was terrible, with lots of lag and hesitation.
I tried driving over a local hill road and almost didn’t make it over, as you couldn’t feed any more throttle into it or it would start to die out.
I checked all the plugs, all very black (I only cleaned them the other day) and a couple of them wet with fuel. I replaced them with new ones, issue remained. I checked all injectors were working (using the “mechanics stethoscope“), they were all firing OK. I reinstalled the air intake back in front of the radiator, no change. I removed and cleaned the cap and rotor, no change. Checked for vacuum leaks around inlet manifold, none. Cleaned idle control valve, no change. Removed idle control valve and bypassed, no change. Re-wired idle control valve as plug was damaged, no change. Resistance tested all leads, all OK. Resistance tested coil, OK.
I thought it might’ve been an ignition issue, so wanted to swap out the ignition amplifier and coil. So I stripped down the coil and amplifier unit, and swapped parts from another unit I had, after thoroughly cleaning all parts.
Curiously in the first photo you can also see an external condenser. This isn’t standard, as there is already a condenser inside the box the coil is mounted to, so someone had added this at some point. It was held on with a zip tie and grounded via a wire wrapped around a screw. I removed it.
This is what’s inside the box of magic tricks. Thanks to Ramon for this image.
I have heard the actual amplifier unit (the rectangular black thing in the top of the box) is a regular cause of failures, so I swapped to another from a spare unit. The standard thermal interface compound that is between the amp and housing its bolted to was almost gone, so I used some computer heatsink compound.
With it all back in the car, did it help? No, the issue remained. Argh.
I then stood back and thought, “damn, it’s almost like when Effie didn’t have enough acceleration enrichment in the tune, I wonder what the ECU is seeing on the MAP sensor”. A quick check on the hand controller, and BAM, the MAP reading was all over the show when the throttle was blipped and wasn’t responding as quickly as it should’ve been.
I removed the vacuum line to the MAP sensor, which also Tees off the FPR (Fuel Pressure Regulator), and inspected it. No cracks, no holes, nothing. I tested it for holding a vacuum with a hand pump, held well. I was about to reinstall it again and admit defeat for the day when suddenly a small dribble of oil came out of the end of the vacuum hose. Well damn, WTF?
I squirted some brake clean down the hose and it took a fair bit to come out the end of the hose. Eventually it came through as solid black, slimey and with some lumps. It took a lot of brake clean to clear the hose and run clear again; lots of oil in the hose.
The hose was refitted, and I fired the car up again. It fired straight up, and the MAP reading on the hand controller was much more stable and quick to respond. A couple of blips of the throttle and there was a little stutter, but once the plugs cleared it showed no signs at all of hesitating when giving it throttle. I took it for a drive, and no matter how hard I came on the throttle, even taking it up a steep hill, she just pulled hard.
So, I probably didn’t need to replace the fuel pump, it obviously wasn’t too bad and was just a coincidence that the car started to run badly when i was low on fuel. The MAP sensor vacuum line, which is the main “load” feed for the ECU was full of blow-by oil. So a tip to anyone that is running a remote map sensor, make sure you keep your vacuum hose clean.
The other interesting fact, is that there is no oil in the hose from either the plenum to the tee, or the hose from the tee to the FPR, or for that matter, in the Tee itself. Only oil in the MAP line. I had a think about this, and suspect the oil has been in there for longer than I have had the car, as when I first got it, the MAP vacuum hose was on its own nipple in the plenum (someone had drilled it out to add a new nipple); when I swapped plenums when I first got the car, the replacement only had the standard single outlet, for the FPR, so I teed off and connected the MAP line to that Tee (the same as I did when I converted Effie to Speeduino). Thus, I can conclude, that the oil had been in the hose for ages and it isn’t new. Its only either gotten thicker and started causing issues now, or had congregated somewhere in the hose and blocked it.
So with that great success I was finally sorted!
The issue was still there. It was small, just a lag coming back on the throttle and an occasional hiccup when taking off from a stop, but it was there. Did the oil get into the MAP sensor?
The next logical step was to remove the ECU and inspect the MAP sensor, and see if there was oil in it. Sure enough, upon inspection, there was indeed oil in the MAP sensor. Lame.
I tried soaking it out with brake clean, and sucking it out with a syringe, but still couldn’t clear it. The trick was to turn the ECU upside down, and gently heat the MAP sensor up so the oil would thin out, and then gravity just drained it out drip by drip.
I cleaned up some surface rust on the ECU bracket, gave it a quick shot of paint and reinstalled.
Testing confirms the issue appears sorted, with no hesitation coming off and on throttle. The throttle response is now snappy and the slight rich mixture it had when coming on throttle is much lessened.
Excellent. Now when I can afford the fuel, I can drive her again.