soontobered84

Is the O2 sensor plugged in good? I had one plugged in, but not all the way plugged in and it made my '89 run like dookey until I got it right. The computers just allowed that the O2 sensor was missing. I unplugged the O2 sensor and plugged it back correctly and then disconnected the battery for a few minutes to reset and "BAM!" I was good.

Rich9928p

Plugging in an EPROM chip backwards will not erase it. The only method of erasing an EPROM is using UV light for a set period of time.

PorKen

True, but it does make the EPROM unusable. I think it fries one of the output or address lines.

76FJ55

Well, I thought I had made some progress over the weekend. As it turns out it was only temporary, but maybe it will invoke more ideas as to the root of my problem. So here is what has transpired since the last update.

I spent Friday night trouble shooting (primarily focusing on the MAF). All the tests I could think to run came up positive for a working MAF. I checked the resistances outlined in the manual I checked the voltages... I check for the reading at pin 6-7 at the LH. Everything looked good, so Sat morning I reassembled the car to take it for a spin. I went to a large open parking lot a couple blocks away for some testing. On the drive there I could already tell it wasn’t running correctly. I believed the car to be running lean so I disconnected the O2 to run open loop and to allow me to hook up my DMM for an indication of what my mixture might be. At Idle I was getting 0.015V from the O2 (extremely lean). Then as I accelerated and RPMs increased the voltage dropped even further to 0.010V, so it was leaning out even worse with load. This confirmed my suspicions that I truly had a mixture problem, so I plugged the O2 back in and took the car back home. As I was confident in my MAF was supplying a good signal I decided to pull the LH chip and go back to the stock chip and FPR to see how it responded. I swapped the chip and FPR back to stock with no other changes. I started the car and took it for a spin. The power was back. Open the throttle and the exhaust note with the X installed was phenomenal and it pulled well all the way to the red. So I concluded it had to be the chip, as the only two items I changed to get the car running well again were the LH chip and FPR. I had already confirmed the FPR operation through monitoring the pressure with the engine off and relay jumped (~58psi) and with engine running; idle at ~45psi, and good response to throttle change, blip the throttle open and press would jump up, and from high RPM close the throttle and pres would drop. The only part left in question, and the part I couldn't test directly was the LH chip. I contacted Ken about a replacement chip, which he graciously agreed to send me, even though he said they usually either work or don't and rarely just perform poorly (well Ken it looks like you are probably right). Still running the factory chip and FPR (new chip not here yet). I drove the car for the last three days remembering how much I enjoy driving it, and totaly thrilled to have it back on the road, but it didn’t last.

I drove it to work this morning and it was running great, at lunch I run out to get a bite, still flawless, but when I came out after eating and got back in it, my exuberance was squelched . I start it up and as I go to pull out of the parking lot, to go back to work, it was blatantly obvious that it has reverted back to its severely under powered condition. The drive home showed no improvement. I haven’t gone back through everything yet, I just took a quick measurement on pin 6-7 to verify the MAF signal and it still appears to be good at the plug to the LH. LH relay jumped; ~1.6v no airflow, increasing v with increasing airflow.

So what happened?
Where’s the failure?
Could it still be the MAF?
Is my LH unstable?
Where do I go from here?
HELP!

Mrmerlin

if you have not swapped in a new MAF do so and test. Also chack all of the grounds engine to chassis battery and the hot post connector and 14 pin connector as well the fuelinjection grounds at the rear of the V

76FJ55

Just took it out for a late night spin. Well, maybe that did it. I went through the ground during this episode, and I had already been through the 14 pin shortly after I initially got the car, so I thought they where all good, but I went through them again. It looked like I may not have gotten all the corrosion out of the female connectors on the 14 pin. So I took apart a Bic pen and used the tail end of the ink tube to lightly knock the corrosion off the inside of the connectors, and sprayed it down real well with contact cleaner, and put everything back together. Fired it up and it's back screaming like a banshee.

Now I'll give it a few days just to make sure it isn't another temporary coincidence, like changing the FPR and chip, but at least this time I did something that would seem to be a relevant fix.

Thanks everyone for all the help. I definitely owe a few of you drinks whenever we get a chance to meet.

76FJ55

Temporary again! So last night after re-cleaning the 14 I started it and it ran great. Took it out around town and on the highway. It had full power, pulled hard all the way through the RPMs... Drove it to work this morning and again it was running like it should. But when I drove it home the problem had re-emerged, and it was way underpowered. The engine still runs smoothly it just doesn't develop any power.

rechecked the14 pin and cleaned it some more but to no avail. Still running like crap.

Man this is frustrating.

SQLGuy

Any chance you're losing one of your ignition coils or coil wires intermittantly?

Don't remember if this was mentioned as a possibility or not? Also not sure whether these cars run badly on four cylinders or don't run at all.

It would be easy to check, though: if you remove one main coil wire and the car doesn't run at all, but with the other one removed instead it's running the same badly as you've been trying to track down, then that would explain it.

76FJ55

I wandered that earlier, but don't think it's dropping a coil. I've put a timing light on plug wires from each coil and they both seem fine.

76FJ55

Okay, so I thought that since I had luck with the 14 previously I would review the wiring diagram and see how I thought it may effect it. after reviewing the schematic I have come to the conclusion that it must have been pure coincidence that it started running well after the the cleaning of the 14 pin. the only wirein the 14 pin that is connected to the LH is the yellow wire at pin #14. all this wire does is send the signal from the starter relay (XIV) to the LH and starter simultaneously, so this wire is not actually sending or receiving from the LH. The LH and the #14 pin both are receiving the signal from the XIV relay, so in essence the 14 pin should have no bearing on the running of the engine. aside from this one wire all the others in the 14 pin are instrument wires and AC wires, all of which shouldn't effect performance. So back to the pondering stage. 14 pin eliminated.

Vlocity

Very frustrating......hang in there.

Do you have your old 02 sensor. I would take a long look at the 02 sensor plug and wires.

Ken
(the other ken...not the smart one)

76FJ55

I do have my original O2. It is still installed in my original exhaust. I do not believe it is the O2 though because I have unplugged it from the harness to for it to run open loop and it made no improvement, and may have actually caused it to get slightly worse. If it were an O2 issue when I forced open loop it should have run reasonably well just without the O2 trim to fine tune the mixture.

76FJ55

on second thought, lets discuss this O2 sensor for a minute. How well/poorly should I expect it to run with the O2 unplugged? upon start up how/when does the LH know to go closed loop? Is there a way to test the O2 directly? I know it produces voltage based on %O in the exhaust, but not knowing where my O2 level is my O2 voltage doesn't mean anything. I know the V is extremely low when the car is performing poorly, but is this an indicator that it is performing poorly because it is extremely lean or is the O2 dead and not sending the correct signal to get the mixture right?

76FJ55

I'm still fighting with this lean condition. So I decided to pick up an Innovate LM-2 to do a little logging. I've been wanting a wideband for some time for other projects as well, so thought I'd use this as an excuse to finally get one. I also installed a new MAF prior to acquiring the LM-2. Below is screen shot of part of my initial run.

A couple of observations I've made so far are:
-The MAF voltage (across pin 6 and 7 of the LH) appears low relative to other posts I found with data log results. (most of them were for SC cars, though I don't think the idle or part throttle should be significantly different)
-I found a post where John Speake referenced the idle should be about 2.6. Mine is about 1.4.
-The MAF voltage does seem to in crease with increasing air flow.
-The WOT switch does cause an enriching shift in the AFR bringing it into the mid 13s (I am running Porken's chips so not sure exactly where it should be, Ken?).
-The WOT doesn't open till virtually 100% throttle. So it needs attention. (WOT contact logged as orange line. 5V=contacts open, 0V=contacts closed or WOT)
-The O2 loop looks to be trying to correct as it will run at close to stoich at cruise, but doesn't seem to be able to compensate at higher airflow settings.
-Idle contact works as evident by the fuel cut when letting off after accel run (lean peak, fuel cut till RPMs drop to ~1400). Porken
-I also logged V between pin 25 at the LH (engine ground) and chassis ground (blue line on graph) to try to verify the integrity of the ground points and ground straps. In general V looked good though there are peaks of up to about .3V max. these peaks are also more heavily concentrated during the WOT segment. I don't know if this is noise, an indication of a faulty ground, or if it is induced by increased current flow in the pin 25 wire. (really rough calculation based on huge assumptions, if there where 10ft of wire between pin 25 and the ground location on the engine, with 18g wire it would take ~4A to cause the .3V drop).
-I also logged Temp II (not shown on the graph) I just logged V as I wasn't sure of the conversion to temp. As expected V tapered off as engine warmed up and stabilized when the engine reached operating temp. If anyone knows the conversion date from V to temp I would appreciate it. I am picking up the temp signal at pin 2 of the LH

Please let me know if you have any suggestions on where to go from here.
Any and all interpretations of the data would be appreciated.
Any suggestions on anything else I should log that would be beneficial, or specific driving cycles I should record?

Mrmerlin

have you checked the grounds at the back of the V?? there are 2 of them and will cause the fuelinjectors to cut out or run poorly. also inspect the Temp 2 wires about 2 to 3 incheches from the connector end, they usually shed insulation and touch, I have replaced a few of these wires at this point best to re connector this part