Jump to content

90 Reatta idle surging after going into closed loop


drdelsol

Recommended Posts

This topic is getting pretty long so I may have forgot... has the crankshaft position sensor been changed?

Link to comment
Share on other sites

It won't make any horsepower apparently. That's the sort of thing that sounds like fuel starvation. When I had my Prom issue I would get a severe bog sometimes and the changes in the running was all over the map. Eventually it failed bad enough it was impossible to ignore. I am trying to think what changes when in gear vs neutral. The ignition timing should tick up a couple of degrees to pick up the load, like 20 degrees to 22 degrees or so. I think EGR becomes active as engine speed increases in gear. Should be nothing at idle. You could unplug that to see if there is a problem there.

  • Like 1
Link to comment
Share on other sites

9 minutes ago, Ronnie said:

This topic is getting pretty long so I may have forgot... has the crankshaft position sensor been changed?

Now that you mention it, Dave had a crank sensor that was loose in the holder and it just went crazy. 

  • Like 1
Link to comment
Share on other sites

I haven't considered the crankshaft sensor because it will start at a touch of the key and idle and rev smooth out of gear. I realized I didn't get a code some I didn't really look at data while it was surging. Going to do that ECM cleaning and then write down and compare sensor data from the good idle and the surging. I admit I could be wrong on crankshaft sensor. I can't think of what might effect it in gear at those revs that doesn't out of gear. It bogs then surges downward pauses around 600 for a sec then dies. Steady pedal pressure won't keep it alive unless go above 2000 but pumping it will a bit. Something with the air fuel. Checked the vacuum lines again and sprayed again and nothing but none look old. Thanks again for all the input

Link to comment
Share on other sites

The only additional comment I have at this point is; as these cars age, failures are occurring that are non traditional with increasing frequency. As I mentioned before, the book says if one of the crank sensor signals is lost while running it will keep running but will not restart. Once broken it should stay that way, but I and others have had experience with self healing crank sensors. I only use the CPS as an example. Other items seem to find a new way to fail we aren't looking for. You had a MAF that worked, didn't work, no code, then it sets a code. How do you diagnose that?

Link to comment
Share on other sites

When my crankshaft position sensor failed the engine sputtered like it was out of time and died. After coasting to a stop at a wide place in the road it cranked back up and ran poorly for a little bit. After that it would try to run but I stopped trying because I was on the side of the road in a safe spot and I didn't' want to take a chance on it quitting at a place where I couldn't get off the road. After doing a little testing I knew it was time to call a tow truck and get it home. My point is, experience has taught us you never rule anything out until you have proven that it's not the problem.

  • Agree 1
Link to comment
Share on other sites

Today went ahead and put in a new crankshaft sensor. No change. Unplug camshaft sensor, no change. Override EGR, it does what it is supposed to do. Still, put it in gear, rev to 12 to 1400 rpms starts jumping, sputtering and dies. Occasional small backfire. Tried data at good idle, seemed ok and when acting bad but I had to keep featuring it around 1500, nothing jumped out at me. Tomorrow I will clean the ECM terminals. Not looking forward to that with my sciatica,  that's a deep footwell. No active codes, once in a while ill get a e26H. Did manage to snap off bottom thread for that shock thing in front of the harmonic balancer

Edited by drdelsol
Link to comment
Share on other sites

You might want to clear the history codes so it only shows recent events. E026 is the catch all Quad driver code, including injectors, TCC, canister purge and EGR. It still looks like fuel starvation or timing that is way off. What dies ignition timing do at the problem RPM? If fuel pressure was checked, what happens to injector pulse width?

Link to comment
Share on other sites

Thanks again.  I have been clearing each time I pull up diagnostics. I just went and got my data. It shows good idle at a little higher but its hard to catch it at low idle easy. It ran bad just at idle for avwhile after reconnecting the battery. At about 900 it showed spark advance 27, pulse width around 6. when I was feathering it around 14-1500 advance was 32 and pulse width  jumping 6.3 to 7.9.

Is there a source for what numbers you are looking for checking E data? I have seen the ranges. Just noticed the new O2 sensor, bosch, was around .70 voltage, moving a bit but the data 18 cross counts were 0. I look at some other threads and some of my numbers match and some don't.

Edited by drdelsol
Link to comment
Share on other sites

5 hours ago, drdelsol said:

Still, put it in gear, rev to 12 to 1400 rpms starts jumping, sputtering and dies. Occasional small backfire. Tried data at good idle, seemed ok and when acting bad but I had to keep featuring it around 1500, nothing jumped out at me.

Have you tried connecting a fuel pressure gauge to the fuel rail and watched what it does when the engine starts jumping a sputtering. If not, you should.

  • Agree 1
Link to comment
Share on other sites

There aren't any hard numbers that I know of just general trends I have seen from years of fooling around with these engines. Warm idle timing around 20deg, a couple degrees more when idling in gear to pick up the load. Timing should advance some as rpms increase. I was looking for a substantially low timing in the problem zone. The pulse width is simply the amount of time the injectors are open, so much like the timing, I was looking for a radical change. That said, if the engine is warm, the pulse width should be pretty steady at a constant rpm. Also, it is dependent on engine load. Because this injection system is timed, the injector open number is for each cycle and isn't a steadily increasing number. If the pulse width is unstable at a constant rpm and load, that does not sound normal? 

Is the readout indicating closed loop? Warm engine, 900 and 1500 rpm points should have the O2 moving around above (rich) and below(lean) ~.450mv  Again, there is no hard number but more cross count is better. Zero isn't good but the conditions to get the O2 hot and active must be met as well.

  • Agree 1
Link to comment
Share on other sites

Didn't get to do much to the car today, I double checked the TPS voltage was correct but I found out that I am getting the same O2 sensor readings whether it was plugged in or not. I still got .43 with ignition only and .69 with engine running and still no cross counts.

Is the computer doing something to give voltage with it unplugged ,even in closed loop or do I have some wiring issue to track down

Link to comment
Share on other sites

My sons 89 had some issues with getting to closed loop and O2 sensor being inoperative a few years ago. The first thing to check is for good continuity between the O2 sensor wire and the ECM. It is a single wire only, purple if my memory is correct. With two people we were actually able to reach from the unplugged O2 wire and the connection at the ECM. I would start there. Plugging, spraying electrical cleaner on the harness connections to the ECM and reconnecting is another good zero dollar check. I am not exactly certain what the offline voltage would be to the O2 but I believe there is always some voltage and it is added or subtracted at the O2. I know I keep saying it but the O2 must be hot for it to work.

Link to comment
Share on other sites

Didn't check the O2 wire today but I did get the fuel tester loan a tool again. 42 lbs key on, 38 or so idle and went it went into closed loop surged and died pressure stayed steady.  Pressure and load test ok but on the leak down it started dropping right away. Fuel regulator looks fairly new and Bosch, no fuel noted in vacuum line. Having problem getting it to idle good long enough to turn all the injectors on and off . Checked the front plugs and they were good with antisieze and conductor gel. Previous guy didn't cheap out far as I can tell. Didn't think it would do anything but disconnected the exhaust to check for backpressure, nothing. But the cat has been replaced too.

Link to comment
Share on other sites

I think your test proved fuel pressure is good enough that it shouldn't be a problem for the engine to run properly. Are you able to drive around without problems with the O2 sensor disconnected? I think disconnecting it should prevent the system from going into closed loop.

 

Link to comment
Share on other sites

After all this, have you tried disconnecting the MAF again?

If the fuel pressure drops relatively quickly on shutdown, it probably leaks internally in the fuel tank. My experience on a warm engine, the fuel pressure rises initially on shutdown as the heat expands the trapped fuel. Some pressure decay is normal over time. You have covered the other problem areas. Fuel pressure certainly doesn't appear to be the problem while running.

It is such a specific rpm band, it would almost seem to be programmed? Getting closer to ECM and/or Prom.

  • Agree 1
Link to comment
Share on other sites

Thanks again for the input. I'll try unplugging those 2 separately again. check the O2 wire and clean the ecm connection. If none of that works I'll try a new ecm. I've had cars with bad coils,bad wires,bad fuel pump,plugged cat etc. but none acted quite like this. My old high school Chevy 350 was much simpler. But that was last century.

Link to comment
Share on other sites

8 minutes ago, drdelsol said:

My old high school Chevy 350 was much simpler

I still drive a 2001 GMC pickup with a V6 for that reason. I like simplicity.

Link to comment
Share on other sites

I just remembered. I did try running it again with the O2 sensor unplugged. It still went into closed loop and died and I got the same data readings on it plugged or unplugged. Guess maybe I should focus on that next.

Link to comment
Share on other sites

That's odd. I'm almost certain when I unplugged  the O2 sensor on mine it stayed in open loop. It's been a long time so I could be wrong.  I'm going to be quite busy today but if I get a chance I will drive mine with the O2 sensor unplugged and see what result I get.

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
×
×
  • Create New...