xennith Posted April 24, 2011 Report Share Posted April 24, 2011 (edited) Ok, I've seen tons of posts about idle issues with the 3.4 DOHC. I've done lots of fixes to it and haven't been able to resolve it yet. It's just a little low and occasionally will stall. If it's sitting in Park you can hear it sort of trip up a bit when you listen to the exhaust, which also smells a bit rich. When driving it gets too low when you stop at a light and eventually will die. Its better but not perfect if you throw in Neutral while stopped. Driving is perfect, this engine doesn't miss a beat. It's been this way since I got it back in October and here is what's been done so far. had a mechanic replace all seals and gaskets, he even pulled the engine to replace torque converter seal and rear main, all new intake and exhaust gaskets. He also did a full tune up including timing belt (but didn't adjust timing chain) new plugs and wires, newer (but not new) EGR, new TPS, new IAC valve, cleaned out the MAP sensor area but it looks new and clean so I kept the old sensor. I haven't had any engine codes come up since the seals were replaced and the EGR was replaced and I've looked for vacuum leaks but so far have not found any. ....was wondering....could it be the catalytic converter? Edited October 19, 2011 by xennith Quote Link to comment Share on other sites More sharing options...
joecutlass Posted April 25, 2011 Report Share Posted April 25, 2011 Fuel pressure regulator? That could give a rich gas smell through the exhaust. Have you tested the fuel pressure? Quote Link to comment Share on other sites More sharing options...
johnny404 Posted April 25, 2011 Report Share Posted April 25, 2011 you need to do a fuel pressure check,preferrably when the problem is happening also dont rule out the maf just because its clean,hook up a scan tool and verify its flowing the correct amount of air obd 1 isnt going to give good data but you should be able to use a tech 1 and watch the values also you may want to remove the injectors while leaving them hooked up and watch the spray pattern if they dont have a nice clean pattern idle quality will suffer,clean them with a good cleaner like bg Quote Link to comment Share on other sites More sharing options...
joecutlass Posted April 25, 2011 Report Share Posted April 25, 2011 You could just use a digital multimeter to test the injectors. A buddy of mine did the spray check and forgot about the spark from the plugs.... car no longer exists. The mulitmwter should test around 13 to 14 ohms. When I had my injector problems, in my 89 cutlass the car wouldn't even run for longer than 3 minutes. Quote Link to comment Share on other sites More sharing options...
xennith Posted June 4, 2011 Author Report Share Posted June 4, 2011 Fuel pressure is 5-12 psi lower than is should be so I'll be replacing the Pressure regulator next week. Hopefully that will fix the idle problem and it'll back to tip top! Quote Link to comment Share on other sites More sharing options...
Crazy K Posted June 4, 2011 Report Share Posted June 4, 2011 no.... You need a more in depth inspection to determine if the fuel regulator is bad. basically... unplug the vac line to it and see if fuel is leaking out the vacuum port. Also you will see a raise in fuel pressure(and a change in engine speed) when the vac line is unplugged(hold the vac line closed), the change is from the regulator allowing fuel pressure to rise and the mixture to enrichen. once you verify that the fuel regulator is fine... I would start with the fuel filter, then the fuel pump if pressure is still too low... Quote Link to comment Share on other sites More sharing options...
xennith Posted October 5, 2011 Author Report Share Posted October 5, 2011 Finally got around to making some changes to the fuel system. Replaced the fuel pump, filter and pressure regulator. I haven't checked the pressure yet but the issue is still there. Seems to idle fine for a few minutes and then just stalls. I swapped the PCM for another from the junk car I had and no change except that it seemed to shift harder than before. The exhaust smells even more rich than before now. I'm thinking its the Cat converter. Any other suggestions? Quote Link to comment Share on other sites More sharing options...
GEN1Z34 Posted October 5, 2011 Report Share Posted October 5, 2011 You said you did'nt replace the MAP, or the EGR with new ones.. I would start with having it scanned @ your local auto parts, most of them with do it for nothing.. No MAF on the 93 LQ1 (OBD1).. Just an IAT in the air filter box. Check the vaccume lines for the fuel vapor purge solenoid, and the solenoid it self as well.. Could be a faulty 02 sensor also.. I would start by having it scanned.. Good luck! Quote Link to comment Share on other sites More sharing options...
xennith Posted October 5, 2011 Author Report Share Posted October 5, 2011 (edited) Could be a faulty 02 sensor also.. Good luck! Better not be, That's new and a PITA to get to! UPDATE: Just did the pressure test. It was right at 39 with key off and at idle. so that seems like it should be ok now, but the original problem still exists. Edited October 6, 2011 by xennith Quote Link to comment Share on other sites More sharing options...
xennith Posted October 17, 2011 Author Report Share Posted October 17, 2011 I replaced the MAP sensor and it does seem much better. I'm not sure its perfect but maybe I'm being overly critical of it. It doesn't seem to want to stall anymore. The guy at autozone said it can take a while for the computer to get used to the new sensor. Is there any truth to that or should a new MAP be an instant fix if it was the problem? Quote Link to comment Share on other sites More sharing options...
AL Posted October 18, 2011 Report Share Posted October 18, 2011 Should be an instant fix Quote Link to comment Share on other sites More sharing options...
GEN1Z34 Posted October 18, 2011 Report Share Posted October 18, 2011 (edited) Should work right away.. OBD2 cars take a few start up and shut down cycles for some codes to clear on their own, as well as idle learn.. ODB1 should be right away.. Edited October 18, 2011 by GEN1Z34 Quote Link to comment Share on other sites More sharing options...
xennith Posted October 19, 2011 Author Report Share Posted October 19, 2011 I recorded it running today. If you listen closely you can hear the engine idle unevenly. It's not shuttering at all now and doesn't stall, but like I said, to me it doesn't seem quite right. Is this how others sound? Its slightly worse in gear, but perfect when driving. Thanks again for all of the info and help. [video=youtube_share;IYtwqbhIKLo]http://youtu.be/IYtwqbhIKLo [video=youtube_share;M73bmYSeTKA]http://youtu.be/M73bmYSeTKA Quote Link to comment Share on other sites More sharing options...
xennith Posted October 21, 2011 Author Report Share Posted October 21, 2011 are the videos clear enough? If not I can try to get better ones. Thanks everyone. Quote Link to comment Share on other sites More sharing options...
GTP091 Posted October 28, 2011 Report Share Posted October 28, 2011 The engine video sounds like an ignition miss what have you replaced on the ignition side??. The exhaust looks more troubling was it cold out or do you have have white smoke coming out. I hope not as it could be steam which means head gaskets. either way your idle seems high what does the tach say? Should idle around 900. Quote Link to comment Share on other sites More sharing options...
xennith Posted November 3, 2011 Author Report Share Posted November 3, 2011 The oil looks clean. No signs of coolant in it. All sorts of gaskets and seals were replaced last February including head gaskets. I can't remember what the weather was like that day. I replaced all plugs and wires, but haven't replaced anything on the ignition pack. I do have a whole set of coil packs and ICM from the parts car I had. Since replacing the MAP sensor it hasn't stalled. The videos are from after that too. Idle is 8-900 in park and usually around 600 stopped in gear, with a slight dip occasionally. The car was cold in the video, won't that make it idle a bit higher until it warms up? Wouldn't a miss throw a code? Quote Link to comment Share on other sites More sharing options...
GEN1Z34 Posted November 3, 2011 Report Share Posted November 3, 2011 Yes it should idle slightly high till it warms up.. Smoke looks like cold vapor burning off not a coolant problem.. The lope in the idle gives me pause though.. What's the deal on your timing belt, how old is it, was it replaced recently? LQ1's properly tuned (obd2) or running correctly with OBD1 should idle consistantly smooth almost rediculasly smooth.. Sounds to me like one of the cam banks has a slight timing issue to me.. Could even be both banks.. Try your coil swap, (i know, it's a bitch) if the issue remains then there's likely a cam timing issue...imo Quote Link to comment Share on other sites More sharing options...
chadz34 Posted November 3, 2011 Report Share Posted November 3, 2011 Yes it should idle slightly high till it warms up.. Smoke looks like cold vapor burning off not a coolant problem.. The lope in the idle gives me pause though.. What's the deal on your timing belt, how old is it, was it replaced recently? LQ1's properly tuned (obd2) or running correctly with OBD1 should idle consistantly smooth almost rediculasly smooth.. Sounds to me like one of the cam banks has a slight timing issue to me.. Could even be both banks.. Try your coil swap, (i know, it's a bitch) if the issue remains then there's likely a cam timing issue...imo I'm gonna disagree with this in part, as an owner of both LQ1's a OBD1 and OBD2, the idle is always by far the worst part on 3.4's.....I find as the engine revs, it is reficulously smooth. At any rate OB1 stock 3.4 should idle at 750rpm and the OB2 3.4 should idle at 900rpm. Quote Link to comment Share on other sites More sharing options...
GEN1Z34 Posted November 3, 2011 Report Share Posted November 3, 2011 I'm gonna disagree with this in part, as an owner of both LQ1's a OBD1 and OBD2, the idle is always by far the worst part on 3.4's.....I find as the engine revs, it is reficulously smooth. At any rate OB1 stock 3.4 should idle at 750rpm and the OB2 3.4 should idle at 900rpm. It's cool.. As owner and builder of LQ1's I can say if the timing is precise @ the cams and there's not some ignition problem or belt/tension issue, I have never had one that would have a stumble in idle or lope.. There are no factory cam grinds availible that can cause such a lope if the timing is factory precise. Though adding a timing spread between the exhaust cam and intake cams can give a substantial lope in idle. As well as having a spread in timing between left and right, (front /rear) cam sets.. Just my .02 Quote Link to comment Share on other sites More sharing options...
xennith Posted November 4, 2011 Author Report Share Posted November 4, 2011 Timing belt was replaced last february with all the other stuff I had done, I can't guarantee that it is correct, but it was done. I may take it back to the guy that did the timing and have him check it again. If the timing was off, would it be noticeable when driving? It's always perfectly smooth when you give it a little gas. Try your coil swap, (i know, it's a bitch) I know this won't be fun, I'll probably wait until it's cold enough that there is no chance to go topless so I can take my time. We've had some beautiful 50-60 degree days here in Cinci and I can't not drive it. LOL Quote Link to comment Share on other sites More sharing options...
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