ej22Buggy Posted March 11, 2015 Share Posted March 11, 2015 Hi everyone! My rig is a rail frame dune buggy with an old legacy an ej22 motor. I built it last year and now I am in the Glamis sand dunes for a week on vacation. I've been having a reoccurring problem with my throttle cutting out under power. It seems to be happening when its hot and idling for a while. The idle will start to stumble and fluctuate. Then when I start to give it gas it hesitates and is like "on-off" when my pedal is down. Sometimes I can get it back to normal under heavy acceleration but other times it is so bad that the engine dies. The problem is only getting worse. Now it happens every time I ride and is really putting a kink in my vacation. I've lurked every thread and forum but have found nothing that matched what I had. If anything, I'm leaning toward a MAF problem. I don't think it could be an IACV problem as it happens with a lot of throttle. I have already replaced the throttle position sensor. I popped the cover off the MAF and re-soldered the 4 contacts to the plug. I don't have access to a new MAF where I am at so it was the best thing I could do. Still nothing. Any help is much appreciated! Thank you in advance! Quote Link to comment Share on other sites More sharing options...
ej22Buggy Posted March 11, 2015 Author Share Posted March 11, 2015 Also there is one code. 22 for knock sensor. I replaced the knock sensor but the code still persists. Quote Link to comment Share on other sites More sharing options...
Fairtax4me Posted March 11, 2015 Share Posted March 11, 2015 You can try unplugging the MAF and starting it and maybe drive it some to see if the problem persists. It may not run well but if the problem goes away MAF may be the cause. If you still have a code for the knock sensor there may be a wiring issue to the sensor or the sensor may not be grounded to the block well enough. The base of the sensor needs clean metal under it for proper grounding. Check the ECU ground wires on the intake manifold. Make sure they're tight. I think its on the lower rear corner of the #4 intake runner on on those older engines. Also check the main engine harness connectors. Make sure they're plugged in all the way. Other things that can cause problems with heat: Igniter module Cam and crank position sensors Fuel pump going out Quote Link to comment Share on other sites More sharing options...
ej22Buggy Posted March 11, 2015 Author Share Posted March 11, 2015 Thanks for the advice! I ran it without the MAF plugged in and the problem still persists. It may be the ignitor module but I'm not sure how to test it other than getting a new one. Quote Link to comment Share on other sites More sharing options...
ej22Buggy Posted March 11, 2015 Author Share Posted March 11, 2015 Fuel pump is an mad and runs constant so I don't think that fuel starvation could be the issue Quote Link to comment Share on other sites More sharing options...
ej22Buggy Posted March 11, 2015 Author Share Posted March 11, 2015 *MSD Quote Link to comment Share on other sites More sharing options...
Fairtax4me Posted March 11, 2015 Share Posted March 11, 2015 (edited) Check connections at the coil and igniter. Make sure the pins are clean and connectors are plugged in all the way. You can also try wiggling the wires while it's running and see if it acts up to see if maybe it's just a loose connection. If you can get access to a fuel pressure guage id suggest checking the fuel pressure just to be sure. Let it run and get heated up and actually drive it with the pressure guage installed. Checking pressure when it is NOT acting up tells you nothing. Need to see if the pressure is steady when it acts up. Edited March 11, 2015 by Fairtax4me Quote Link to comment Share on other sites More sharing options...
plogerjb Posted March 13, 2015 Share Posted March 13, 2015 Wild guess here, but cam and crank position sensors are a common failure part under hot conditions and will often cause intermittent issues. Difficult to check without a high end scanner or oscilloscope though. Quote Link to comment Share on other sites More sharing options...
ej22Buggy Posted May 26, 2015 Author Share Posted May 26, 2015 (edited) Hi again guys. After returning from my trip I have since replaced the MAF unit and fixed the knock sensor issue by improving the wiring (soldering instead of crimping). My throttle cut issue is still present. It seems to happen after the engine has been running for some time (maybe 30 min?) and likes to act up when it has been idling for some time (like putting down hill) and I tell you nothing is scarier than trying to climb a steep dirt/rocky hill with the throttle cutting at 1 sec. intervals. Usually I can get it to stop with some full-throttle acceleration. Fuel pump is not the issue as I hear it buzzing away the same as it always does (its right behind me). I checked the wiring to all the plugs, everything is good. Do ignitors go bad in these engines? Coil packs? ECUs? O2 sensor? Also, my idle has suddenly become VERY low and the engine will even stall. Am I looking at a ECU issue? Do they go bad? Or throttle POS? IACV? EDIT: I got the ignitor module from a junkyard (because my motor didn't come with one) and it was out of a manual car (my engine/ecu was from an auto). Would this matter? I see it listed as 2 different parts online. Edited May 26, 2015 by ej22Buggy Quote Link to comment Share on other sites More sharing options...
1 Lucky Texan Posted May 26, 2015 Share Posted May 26, 2015 (edited) could this be an intermittent crank position sensor? some older soobs had those go out at temp i think. do you run without TB covers by chance? maybe some metal filings/debris have collected on the CPS. also, kinda wonder if the TPS could an issue here? Edited May 26, 2015 by 1 Lucky Texan Quote Link to comment Share on other sites More sharing options...
ej22Buggy Posted May 27, 2015 Author Share Posted May 27, 2015 could this be an intermittent crank position sensor? some older soobs had those go out at temp i think. do you run without TB covers by chance? maybe some metal filings/debris have collected on the CPS. also, kinda wonder if the TPS could an issue here? But if it was the crank sensor, would that even be able to cause the throttle to completely cut out? Also it is not throwing a code. By "TB covers" do you mean the plastic vanity cover? -yes I do And what does CPS stand for? The throttle position sensor has been replaced (by one from a junkyard) but the problem still persists. Quote Link to comment Share on other sites More sharing options...
ej22Buggy Posted May 27, 2015 Author Share Posted May 27, 2015 If its any help, here is how my engine is currently set up, Maybe there is something obvious that I am missing. Quote Link to comment Share on other sites More sharing options...
1 Lucky Texan Posted May 27, 2015 Share Posted May 27, 2015 CPS - crank pos sensor hmmm...might be worth scanning for pending codes. Particularly right after a failure. Some codes must occur 2-3 times before the MIL is lit. triple check all grounds and sensor/harness connections. Quote Link to comment Share on other sites More sharing options...
ej22Buggy Posted May 27, 2015 Author Share Posted May 27, 2015 Oh now I see what you mean. (TB = Timing belt, not Throttle body). Alright, I will do that. Thanks for the advice! Quote Link to comment Share on other sites More sharing options...
Fairtax4me Posted May 28, 2015 Share Posted May 28, 2015 If it's sitting at idle and starts doing its stumble thing, will it eventually just cut off? Or does it have to be driving for the problem to happen? Quote Link to comment Share on other sites More sharing options...
ej22Buggy Posted June 2, 2015 Author Share Posted June 2, 2015 If it's sitting at idle and starts doing its stumble thing, will it eventually just cut off? Or does it have to be driving for the problem to happen? After sitting at idle for a while, it will sort-of hiccup a bit and sometimes get close to dying. When it starts doing this, the throttle will start cutting out under acceleration. Its almost like the a/f ratio gets out of whack. I've pulled the plugs after this happened and they were white (too lean?). Quote Link to comment Share on other sites More sharing options...
Fairtax4me Posted June 2, 2015 Share Posted June 2, 2015 Have you out a fuel pressure guage on it yet? Quote Link to comment Share on other sites More sharing options...
ej22Buggy Posted June 4, 2015 Author Share Posted June 4, 2015 Have you out a fuel pressure guage on it yet? No I have not. But it seems unlikely to be a fuel issue as it does not sputter before it cuts. It is literally on-off. If the fuel pump just stopped I assume it would sputter a bit before it lost power. Here is the fuel pump I am using: http://www.summitracing.com/parts/msd-2225?seid=srese1&gclid=CO_224Kf9sUCFcURHwodXK0Apw It is more than enough to run the ej22. Also, the problem tends to happen when it idles for a bit (the fuel pump will hum along just as it always does, no change). If it was low fuel pressure it would be erratic and have no correlation to what the engine is doing. It really seems like an ignition issue. But could just as likely be the computer cutting spark for some reason. Quote Link to comment Share on other sites More sharing options...
Fairtax4me Posted June 4, 2015 Share Posted June 4, 2015 You never know until you put a guage on it. I had a Chevy 2500 that would start and run ok, it could be driven a short time and then it would die immediately if you hit the gas. Fuel pump was running and making that loud Chevy fuel pump whine the whole time. Was making about 5 psi. If you're convinced its a sensor /igniter issue, go to a junkyard and grab all the sensors off of a car with matching engine. Doesn't take long to swap all of them one at a time until you find one that cures the issue. Quote Link to comment Share on other sites More sharing options...
ej22Buggy Posted June 4, 2015 Author Share Posted June 4, 2015 Do you use any special gauge for measuring fuel pressure or will any gauge work? The only other sensor/electrical that could be an issue would be an ignitor i guess. Another trip to the junkyard is in order. Thanks again for the advice! Quote Link to comment Share on other sites More sharing options...
ej22Buggy Posted June 16, 2015 Author Share Posted June 16, 2015 Well I may have stumbled across the root of the problem. After doing some more research, I learned a lot more about the throttle position sensor and how the computer responds to it. There are a set of contacts (pins 1 and 2 on the TPS) that should be closed at idle and open when throttled. Hooking up my multimeter, I realized that the contacts never closed. All this time the engine was actually at a fraction of throttle when it was "idling". The butterfly valve was being held slightly open by the top adjustment screw (which shouldn't be used at all). So, I followed the haynes instruction that details the TPS adjustment. Using a feeler gauge, I set the sensor so that the contacts were closed at .028" and open at .035" from the lower bump stop/screw. After the adjustment I started up the engine and it settled to 750 rpm after a few minutes. However, when I gave it gas and let off, the RPMs would dive to ~500 and work back up to 750. I proceeded to remove the idle air valve and give it a good cleaning with throttle body cleaner. I was amazed how much gunk was in there! After reassembling, I started her up and it idled better than ever. I blipped the throttle and the RPMs dropped to 1000 before working down to 750... perfect! Maybe this could have been causing my throttle cutting? I believe it might be the source of the problem since it was always initiated by the engine idling (or what I thought was idling) after it had been running a while. I also replaced the ignitor and ECU water temperature sensor (just in case). And to address the possibility of low fuel pressure, I hooked the fuel pump relay to ignition power so that it will always be running, eliminating the possibility of the ECU shutting it off while it is running. Now all I need to do is wait for a nice day to test it out! Quote Link to comment Share on other sites More sharing options...
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