djbrown01

I was on my way to work this morning and the Speedo died and then immediately came back on, and then the rpms dropped to zero, pulled over and hit the key and nothing happened.. waited a couple minutes and tried again, this time it cranked but wouldn't catch, next time I gave it a little gas it started up and would idle fine.. back on the road as I was up to speed I could feel the car jerk and then regain the power, it got worse to the point that it died again, restarted fine and I made it to work.. this is a 1995 with 197k miles and now when I start it at idle you can hear it missing. ecu was fixed and that's about all I've done to it since I owned it.. does anyone have any suggestions on what to look for? I've heard tps, mass air, ecu like always, but nobody mentioned anything about the speedometer dying and then coming back? possibly the battery? bad ground?

fixmiester

Sounds like a fuel problem, but the speedo issue would be too much of a coincidence, so I would suspect an electrical cause. If the car idles, get a meter and measure the battery voltage without any significant loads. It should measure measure between 13.0 and 14.5 volts at idle. Then turn on A/C and headlights; it should measure at least 13.0 volts at idle. The fact that it cranks okay now, but didn't at first suggests a bad connection from the battery cabling, so you'll need to look at everything, wriggle cables, etc. and see if anything is suspect. Missing while idling could be very low voltage to the coils--again, caused by battery or poor connections. The fact that it didn't crank at first would indicate that ecu/tps/MAF, etc. are not the root cause. Any codes?

LScowboyLS

my suspicion is that ECU was fixed but not correctly

djbrown01

I would have thought the same but it's been in the car for over six months with issue up to this point, I'll definitely be checking the battery voltage as soon as I get out of work

timmy0tool

iTrader: (7)

ECU is a very good suspect but i would check the small things first like the battery terminals. make sure they are tight. also check if there is power steering fluid dripping onto the alternator (common). the ps reservoir and pump sits directly above the alternator and can leak. a compromised alternator will cause some of your issues.

djbrown01

oddly enough I pulled the negative cable off earlier to see what it would do without it and it continued running and pretty much ran the same way as when it was on

fixmiester

Don't do that!!! The battery acts like a huge transient voltage filter to all kinds of spikes produced by myriad devices in the car. Disconnecting either cable while running: You might as well play Russian Roulette.

LScowboyLS

this is exactly right!!


also, one of the signs of an ECU fix done wrong is that it only lasts a few months

I will put it to you this way, I have now opened up hundreds of ECU's and everyone that has been previously repaired was done incorrectly (usually incorrect type of capacitors)

Yamae

Both the speedo and the tachometer are indicating the number of pulses from the ECU converting the number to be the rotation of needles. The zero indication of both would be caused by the ECU, the meter units themselves at the cluster or the cables.

As LScowboyLS mentioned, many re-builders of the ECU don't use low ESR capacitors and that cause the problem again soon.

We must know that why Toyota had to use electrolytic capacitors that contain the quaternaty ammonium salt which was rather risky. In order to get good performances like a better noise rejection and a better ripple rejection, they had to use those capacitors because low ESR electrolytic capacitors were not widely available other than those that contain quaternaty ammonium salt at that time.

To use regular type of electrolytic capacitors causes the insufficient noise rejection as well as the poor ripple rejection. This causes the malfunction of the ECU often. I hope your ECU is not causing this problem.

djbrown01

I bought the capacitors myself from the list that was put up on this forum, and here's another bit to the issue. last night after work I was checking battery terminals and things and found the positive one cracked, switched it out and thought it was all good, on the way home it did the same thing, so I swapped the computer out for another one that I had at the house.. this computer was the one that came in the car that I had took out before when I was having random misfire issues and had a different one rebuilt. last night after installing the commuter that wasn't rebuilt I took it for a long drive and all was good.

now to this morning I start it up and immediately the car is searching for idle, missing, just running completely terrible, much worse than it was yesterday with the rebuilt ecu.. I'm lost at sea here and don't know where to look next, other than putting the rebuilt ecu back in

fixmiester

Did you ever run the voltage checks I mentioned?

djbrown01

voltage checked out fine with everything, this is aggravating and I need to get it fixed, I don't know how it can go from fine last night for thirty miles to even worse than it was before

LScowboyLS

sometimes by the time you fix the failed capacitors on an ECU, they have already leaked to such a degree that the corrosive effects of the leaking failed electrolyte will have permanently ruined the electrical circuit traces in the circuit board itself, at that point you must find an ECU on ebay or the junkyard that has not been previously repaired and also has not leaked yet and then have that better condition ECU properly rebuilt with new capacitors

djbrown01

ok well I didn't go the route sending it to cowboy. I bought a remanufactured unit and I'm guessing it's not that because the car is doing the exact same thing.. mostly the issue right now is when you are on the highway it feels like the fuel is being cut off, the car noses over for a second and then picks back up.. it's not a misfire at all, car runs perfect at idle and under about fifty mph.. after that it decides it wants to cut the fuel is what it feels like to me.. it did just set code p0420 and I do have an exhaust leak and a broken egr pipe, the throttle body looks to have a lot of buildup on the backside of the butterfly.. I'm lost still

djbrown01

and at idle it only seems to miss around the 2500 and up range :-(