ORCA Posted August 17, 2006 Share Posted August 17, 2006 i posted this in the NAXJA tech forum but I really think I can get as much help as I can... (here's the thread if you give a rats @$$: http://www.naxja.org/forum/showthread.php?t=94226 ) So last week I did a good amount of work on the heep (borla header, poly motormounts, new cap, new rotor, new plugs, new vac lines, new CCV lines, oil/filter change, and a k&n "cold air"). Got the truck running fine with all these new additions (the best it's been running in a while in fact). Went on a short trail (about 4.5 miles total) and the truck performed amazingly and eventually drove it home alright. The next day I started it up and it idled fine. As soon as I stepped on the gas the engine began to run really rough and eventually died. It then wouldn't start after that. I checked all the vacuum lines and electrical connections and everything was ok. I wiggled the injectors and tried starting it again, and it did. This time it idled fine for a minute and then ran rough and died (no throttle applied). I just tested the TPS today following both a haynes and chilton manual. If I performed the test correctly, then according to those books the TPS is bad. I got a reading of around 4.8 volts which was constant from closed throttle to wide open (and everything in between). I'll go out and double check it tonight. So say the TPS is bad...would that cause the no start? If it is bad, is it a dealership part or could I get away with one from pick n pull..? Also..I remeber partially while I was swapping out the old header and putting in the borla, I briefly cleaned the o2 sensor with carb cleaner. Would this destroy it? If so, would it cause the problems i'm describing? I'm a pretty competent home mechanic, but this has throughly stumped me. I'm searching this site and my haynes/chilton manuals like a mad man trying to get my damn truck running!! Any help is, as always, greatly appreciated Also, which two wires do I test on the TPS? Blue and gray? :hateputers: Link to comment Share on other sites More sharing options...
feerocknok Posted August 17, 2006 Share Posted August 17, 2006 A bad TPS will pretty much screw everything up. You can snag one from the JY, and hope that it's not bad as well, or get one from the stealership for an arm and a leg. That's all I have to chime in. Link to comment Share on other sites More sharing options...
ORCA Posted August 17, 2006 Author Share Posted August 17, 2006 I suspected that a bad TPS would cause the truck to not start. But I hope to get some good advice before I throw money at it. (oh and their only $92 at kragens, according to their website). Link to comment Share on other sites More sharing options...
feerocknok Posted August 17, 2006 Share Posted August 17, 2006 A buddy of mine got his from a NAXJA guy for $25 shipped. The guy totalled it, and was parting everything. If you can't find one at the JY, check something like that out. Link to comment Share on other sites More sharing options...
ORCA Posted August 17, 2006 Author Share Posted August 17, 2006 UPDATE: I finally tested the TPS the correct way and it appears to be in working order. So that's probably not it..maybe ignition coil? Or a fuel delivery problem? Link to comment Share on other sites More sharing options...
Bounty Hunter Posted August 17, 2006 Share Posted August 17, 2006 Have you replaced all the injector o-rings? My '88 4.0L had a problem of quenching the plugs with fuel. Was a bad IAC motor on the throttle body. Link to comment Share on other sites More sharing options...
ORCA Posted August 17, 2006 Author Share Posted August 17, 2006 Actually I didn't when I replaced the head... :nuts: Would that cause it to not start? Link to comment Share on other sites More sharing options...
BIGHEEP Posted August 17, 2006 Share Posted August 17, 2006 I had a similar problem on another vehicle and it was a bad O2 sensor. Link to comment Share on other sites More sharing options...
pingpong Posted August 17, 2006 Share Posted August 17, 2006 To me it sounds as if the fuel problem. Lets analyze this though. Check for compression, I am going to assume this is there. then check for spark. Check for it all the way down to the plugs, or just pull a plug and turn it over. if it checks out then it is on to the last thing FUEL I have had a MJ run and idle fine, but as soon as you give it gas it would die out. also if it idle for more then a few minutes it would die. Ended up being a bad fuel pump. I would check to make sure that I had adequate fuel pressure on the rail, and if all that checks out.. I can't tell you what else to check Link to comment Share on other sites More sharing options...
rbostoncaxjmj Posted August 17, 2006 Share Posted August 17, 2006 Hit your starter with a hammer! See what happens! I have an 88, and it has happended to me more than once. 1) Driving fine day before. All of a sudden next day, dead. Won't start. Took the hammer and whacked the starter; off it started! 2) Months later, driving fine again. All of a sudden drive was rough, and it just died (may be fuel related or not). But Won't start after that (suspect combo problem fuel related and starter). I hit the starter with the hammer next day (after going thru what you did....checking TPS, etc...) and it just started. Finally got it running; took it back to the garage. Didn't find any fuel related problem. One other suggestion. Another time I had "no start" again. Whacking the starter didn't help. Turned out to be the CPS. Replaced mine and walla - she started up again! Good luck! Link to comment Share on other sites More sharing options...
mjeff87 Posted August 17, 2006 Share Posted August 17, 2006 I would suspect the O2 sensor is hosed, but if you're trying to start it cold that shouldn't matter. The ECU stays in open loop until the engine warms up, then starts adjusting A/F based on sensors. Try disconnecting it just for kicks and see if it fires :D I had an O2 go bad on my MJ last year and it caused all kinds of random poor running/cutting off problems. I checked everything and couldn't find the cause, and started disconnecting sensors one at a time to see if any had an effect. CPS and MAP sensors killed the engine immediately, TPS just caused more wacky running, but when I pulled the O2 off everything cleared up. I ran with it discoed for about a month, then one day hooked it back up and it didn't change anything....still ran (runs) good. So I left it connected :nuts: Do like Pat says and start with the basics (air, fuel, spark, compression) Jeff Link to comment Share on other sites More sharing options...
ORCA Posted August 18, 2006 Author Share Posted August 18, 2006 Replaced the o2 sensor and it runs! Thanks guys. Wish I knew not to clean the damn things.... :roll: Anyway/ i've got a new CPS and injector orings on the way too, so hopefully it'll be back to running cherry. :cheers: Thanks again fellas. :chillin: Link to comment Share on other sites More sharing options...
partsmj Posted August 18, 2006 Share Posted August 18, 2006 The factory TPS for the automatics, PN 33004650 87-90 is now $37 retail. They have around 3800 left in Milwaukee. I will be buying a few for stock. The manual trans TPS PN 33003194 is $129 and about 250 left. Link to comment Share on other sites More sharing options...
Kenosha Warrior Posted August 18, 2006 Share Posted August 18, 2006 ugh, the o2 sensor in my MJ makes it belch flames from the tailpipe. Hi-Ho,Hi-Ho, its off the JY we go! Link to comment Share on other sites More sharing options...
Recommended Posts
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 accountSign in
Already have an account? Sign in here.
Sign In Now