edselsouth1 Posted June 28, 2011 Share Posted June 28, 2011 We had a similar problem with a 1994 Pontiac Trans Sport, 3800 engine. Sometimes it would run good, sometimes not. Same for starting. Turned out to be the electrical part of the ignition switch (mounts on column housing under dash). Replacing the switch and the wiring harness plug-in cured the problem. This same problem has since occured on my other Trans Sport (1992), so that's the first place I looked. Just a thought. David. Link to comment Share on other sites More sharing options...
DAVES89 Posted June 28, 2011 Share Posted June 28, 2011 I'm going to Gibson's on Wed. to see what is out there [and see what Jim Finn left behind since he came thru]. So if you need anything let me know. Totally off the wall, but my idle control sensor is acting up [but my idle is increasing] could that be what is causing yours to cut out? Link to comment Share on other sites More sharing options...
2seater Posted June 28, 2011 Author Share Posted June 28, 2011 Edsel, I have wondered about that possibility also. I have not been able to recreate the engine stoppage by closing the drivers door or hood, which it did originally. That would have made more sense than the CPS regarding a small vibration causing a stall. I will look into that also as the key is hard to turn, on occasion, for no apparent reason. However, wiggling the key and slapping the lower steering column doesn't seem to have any effect?Padgett mentioned an O'scope, which I do not have, but it got me to thinking about the VOM I mentioned. It came with a cable and software to use it connected to a computer, where it will display, record and graph the recordings, which can be done for extended periods of time. This is a screen shot of the meter operation on an old notebook computer I have downgraded to garage use. This is the same computer that has my TunerPro software and files to connect to the car for recording and readout from the ALDL, also for extended periods of time. The graphical screenshot is not really amplitude of the 18x signal, it is the change in frequency as the engine idles. I would think, it would also give an indication of the signal while the engine is cranked for a situation where the engine will not start? Link to comment Share on other sites More sharing options...
2seater Posted June 30, 2011 Author Share Posted June 30, 2011 Dave, I never got back to you regarding the '89 Eprom in a '90 model but the chip sounds even newer than mine (ANWU) and my '90 was built in 1989, so maybe early models carried older designation chips?In any case, I am stumped. I cannot make the car fail no matter what I do. I have not disconnected or modified anything aside from the original battery and associated connections in that area. I thought I had it fixed at that point but it failed last weekend but always revived itself. I have wiggled, tapped and pulled on everything I can find. I have the lower instrument panel and console removed so I can access all of the boxes, connections and ignition switch. I ran the engine for 1/2 hour with a blow dryer heating the CPS, and today I heated the ECM to an internal temperature of 136 deg.F and also let it run for 1/2 hour, nothing happened. Idle remains good, fuel pressure stable @ 37 psi, steady engine vacuum @ 18" and timing of 19deg. I have tried "hot soaks" of 5-10 minutes several times but it never fails to start and run smoothly. The one thing that has changed is the check engine light and associated knock sensor code is gone. The only other unanswered question is the 3X signal from the CPS. I still get something like 9X or about 1/2 of the 18X signal? Is some of the divide-by circuitry in the ICM and the signal from the sensor itself is more "raw"? I am tempted to go ahead and replace the CPS as I have a new one and the symptoms are classic CPS failure. Replacing it by the side of the road would be impossible but plugging in a replacement ECM is no problem. To paraphrase "If it ain't broke, you can't fix it". Link to comment Share on other sites More sharing options...
padgett Posted June 30, 2011 Share Posted June 30, 2011 (edited) Nano arrived last night. Everything you need to check CPS/MAF and less. Comes with a nice x10 probe. Is somewhat delicate but tiny. Edited June 30, 2011 by padgett (see edit history) Link to comment Share on other sites More sharing options...
Guest Mc_Reatta Posted June 30, 2011 Share Posted June 30, 2011 Hard to say if the information you read for the 3X pulse is because of a problem with the sensor and shutter ring or it is due to the interpretation that your frequency meter displays. This pulse is not a uniform signal like the 18X signal from the sensor is. (equal length high and lows of uniform cycle, but 3 differing brief highs followed by 3 variable but much longer duration lows).Your meter may be trying to interpret this signal into something more regular over the period of time it uses to analyze the signal and giving a readout that is not indicative of the actual signal. Need to know more of how your meter "thinks" and how the measurement is set up to be read. That's why an o scope is the preferred instrument to use for this. In either case, this 3X signal is only needed at start up and is not necessary in order for the engine to continue running. It is not passed on to the ECM and neither is the 18X signal. They are only read by the ICM which then creates a different regular 3X signal that is passed on to the ECM to use for the RPM calculation and to determine spark advance and how to fire the injectors. So your inability to get the engine to start could be any either the ICM or CPS and lack of any of the associated signals, the stuttering and stalling while running from closing the doors and hood etc would not be due to the 3X CPS signal but still could be from the 18X signal or the ICM.May want to pursue trying Padgett's suggested o scope to further analyze these signals, or just replace the ICM and CPS with good replacements. Should also check the integrity of the wiring between the CPS and the ICM to verify there is not an intermittent due to a defective wire.Padgett, what signal are you displaying on the Nano in that picture? Link to comment Share on other sites More sharing options...
padgett Posted June 30, 2011 Share Posted June 30, 2011 (edited) That was just the onboard reference. The capacitance effect is because there is no ground.BTW do not try to use an O'scope on the coil spark plug terminals - quick way to blow circuits unless designed to handle 60-100,000 volts. Edited June 30, 2011 by padgett (see edit history) Link to comment Share on other sites More sharing options...
Guest Mc_Reatta Posted June 30, 2011 Share Posted June 30, 2011 Looks like a useful addition to one's toolbox.What do they claim is the upper frequency limit it can display? Link to comment Share on other sites More sharing options...
DAVES89 Posted June 30, 2011 Share Posted June 30, 2011 Just got back from Gibson's. Did pretty good. I got another ECM with the e prom code ASSU from an '89 Reatta. I also grabbed from the other '89 Reatta the prom only. That code is ASSW. Are those the rigt proms for the 89's? Neither car was running. The one I took the prom only was just full of mouse nests and mouse droppings. What a mess... Link to comment Share on other sites More sharing options...
2seater Posted June 30, 2011 Author Share Posted June 30, 2011 Padgett, nice little unit. I will put that on my wish list. It looks like about the same money as my VOM, but with a different capability. I absolutely agree that the O'scope is preferred for this type of asymetric signal, but I used what I had. I suspect as long as a variable signal is outputted the CPS is working but the added detail would be nice to have. Mc, the meter sampling rate is selectable but it is never very fast, once or twice per second max. Your conjecture about the meter "smoothing" the readout sounds logical. It wouldn't be quite as bad if it would give an indication it is about to fail, like a bobble or hiccup, but it doesn't. It simply shut off with no warning, just like the key was turned off. The comment about only the CPS and ICM being used for start and running got me thinking about the dash, which stayed on when it quits. I think there are different circuits in the ignition switch that power different items, but that would lead me to believe it isn't related to the ignition switch itself.I do appreciate the insight and comments. Link to comment Share on other sites More sharing options...
padgett Posted June 30, 2011 Share Posted June 30, 2011 Well, in general the only thing that shuts off like a switch is electrical. Fuel issue will usually be a bit slower.BTW they claim 1 MHZ but one review said the waveforms distort above about 500 khz. This weekend I'll see what MAF and CPS look like. Just need to dig out my BOB.This new orphan is being quite needy and a good example of trading time for dollars. First on the list is new hood struts but those should be available locally. Know it needs a fuel pump/filter/tank slosh so that will be second. And then the new compressor and flush just showed up for the blue so I can get that back together. Full weekend but monsoon season seems to be here so temperatures are down. Link to comment Share on other sites More sharing options...
2seater Posted June 30, 2011 Author Share Posted June 30, 2011 It sounds like it should work well for automotive testing. It certainly is priced right and is convenient. MAF range is 2.0-10.4kHz. It will be interesting to see your results. I did pull the CPS and physically it looks fine. I checked the resistance between pins just to see if different between new and old sensors and they are, by a lot. No science involved, just comparison of two parts. Maybe there is something there, maybe not? Link to comment Share on other sites More sharing options...
padgett Posted July 1, 2011 Share Posted July 1, 2011 Well here is a MAF at about 750rpm warm idle. Can read all sorts of things around the periphery, this gadget is neat. Was hard to hold it and the camera steady without flash. Need to find the BOB to get a CPS display and have two sick cars at the moment. Link to comment Share on other sites More sharing options...
DAVES89 Posted July 2, 2011 Share Posted July 2, 2011 Can someone tell me if I got the right coded eprom [assu assw] for my '89s? Link to comment Share on other sites More sharing options...
padgett Posted July 2, 2011 Share Posted July 2, 2011 ASSU is 89 Riviera with 2.97 axle and federal emissions, ASSW is the same with Califonia emissions. Both are ECM proms. Looking at the TSB for the replacement (90-6F-8), the same replacement is used for both Riv and ReattaIf you download the '93 P&A from reatta.net it is on page 3-24 group 3.670 Link to comment Share on other sites More sharing options...
2seater Posted July 10, 2011 Author Share Posted July 10, 2011 I just got back to the problem child and I did find the signal from the new CPS is now different than before, but still confusing. The 18x shows 1.2 kHz at a slightly elevated idle and the 3x shows 60Hz. I didn't save a copy of the original signal for the CPS, (damn), so I can't compare to see if I read it wrong. Padgett, any chance you could try your new magic box on those two signals to see what it should look like? I am definitely move that item up on the list. Link to comment Share on other sites More sharing options...
padgett Posted July 11, 2011 Share Posted July 11, 2011 Is just a matter of finding my break out box, unfortunately have been overwhelmed with a/cs and gas tanks lately and I *think* I know about a 30 cubic foot area it may be in. Link to comment Share on other sites More sharing options...
2seater Posted July 11, 2011 Author Share Posted July 11, 2011 Yes, I understand. I have followed your tale of woe also. I think I will just drive it and see what happens. It's one of those things that probably doesn't mean much, since it appears to work. But, the inconsistant/confusing info I have gathered is either showing there is a difference between sensors, or, the meter is incapable of displaying useful information? Unless something more concrete shows up, it is going to take a long time for me to be comfortable with the durned thang. Link to comment Share on other sites More sharing options...
2seater Posted July 20, 2011 Author Share Posted July 20, 2011 Well, a week has elapsed and the car hasn't missed a beat. Good, I guess. The only other thing I replaced, aside from the CPS, was the EEPROM in the ECM. I installed the one from the ECM I purchased from Master Finn. No real change there although it does appear to have lost about 1/2"Hg of idle vacuum. Coincidence? Maybe a slightly lower commanded idle speed?I did buy a Nano V1 o'scope. Neat little item, but to a novice, hard to understand and the manual was certainly written/translated by someone that doesn't use english as a primary language. I found this website that describes the operation, sort of "For Dummies" videos and also a free software upgrade from a Ben F. The software upgrade improves the functionality, appearance and a (19) page manual that is a vast improvement over the one included with the unit. The new software automates some of the setup functions,changes the command keys and expands the commands with sub-menus:Using the DSO Nano pocket storage oscilloscope | Hey, James! How do I … ? Link to comment Share on other sites More sharing options...
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