Megadan Posted March 1, 2016 Share Posted March 1, 2016 Over the winter my truck has developed this issue where below operating temp (even on rare occasion even warmed up), between 2300-2800rpm at part throttle it will act like it just loses all ignition timing, tumbles, bumbles, backfires, and stumbles. I just spent this last weekend checking every ground, connector, cleaned my IAT sensor, put on a new TPS I had sitting in a box and calibrated it, swapped out map sensor (No change), My truck runs better than it has in many months. Short of Eliminating the C101 (which is my next plan) I have done every and any Cruiser tip. Truck has no EGR. Fuel pressure is rock solid.Now, I know it's not fuel. How? Because when it starts to stumble I can floor it and my truck takes off like a raped ape. Other than that specific thing it does, it idles fine, runs fine, fuel econ hasn't changed much (and actually improved after putting on new vacuum hoses woot). Yet no matter what I do, at that very specific Rpm range, and not even very consistently, it just decides to go beserk.Is there a chance that a CPS could give just a weak enough signal to cause the ignition timing to go wacky, but still allow it to start and run fine otherwise? Most people talk about them failing like a light switch. I am just wondering if maybe my new clutch and flywheel has stuck some material on the end of that magent. If so, why would it have an effect on just that very specific point and nowhere else...Edit: I would also like to note that the truck has a new distributor, and new enough coil and ICM to consider them new. (less than 5000 miles) Link to comment Share on other sites More sharing options...
cruiser54 Posted March 1, 2016 Share Posted March 1, 2016 Is the injector harness rubbing on the rearmost head bolt? Link to comment Share on other sites More sharing options...
Megadan Posted March 1, 2016 Author Share Posted March 1, 2016 No, it's actually got a good amount of clearance and all of the wiring is well shielded with tape and/or sheathing. Link to comment Share on other sites More sharing options...
xjrev10 Posted March 2, 2016 Share Posted March 2, 2016 I'm having sort of the same issue.... I was just gonna post a thread. All new grounds, yellow injectors, no vacuum leaks, all connectors tight... New fuel filter, pressure regulator... Getting frustrated. I don't have a tach but it seems like around the same rpm all the time.. Next plan is new cap/rotor/wires/coil. Plugs are new.. Link to comment Share on other sites More sharing options...
Megadan Posted March 2, 2016 Author Share Posted March 2, 2016 I'm having sort of the same issue.... I was just gonna post a thread. All new grounds, yellow injectors, no vacuum leaks, all connectors tight... New fuel filter, pressure regulator... Getting frustrated. I don't have a tach but it seems like around the same rpm all the time.. Next plan is new cap/rotor/wires/coil. Plugs are new.. I can't say for sure I have no Vacuum leaks as my current brake booster may be a culprit for mine, but I attribute that leak with a different issue it has, and it only happens when I first touch the brake pedal. It's supposed to be nice this weekend, so I plan on removing and cleaning off the CPS. I may trace and go over the ignition wiring in the harness and if I have the time to eliminate the C101. Link to comment Share on other sites More sharing options...
cruiser54 Posted March 2, 2016 Share Posted March 2, 2016 I'm having sort of the same issue.... I was just gonna post a thread. All new grounds, yellow injectors, no vacuum leaks, all connectors tight... New fuel filter, pressure regulator... Getting frustrated. I don't have a tach but it seems like around the same rpm all the time.. Next plan is new cap/rotor/wires/coil. Plugs are new.. I can't say for sure I have no Vacuum leaks as my current brake booster may be a culprit for mine, but I attribute that leak with a different issue it has, and it only happens when I first touch the brake pedal. It's supposed to be nice this weekend, so I plan on removing and cleaning off the CPS. I may trace and go over the ignition wiring in the harness and if I have the time to eliminate the C101. Plan on 2 hours for the c101 elimination and take your time!! Link to comment Share on other sites More sharing options...
cruiser54 Posted March 2, 2016 Share Posted March 2, 2016 I'm having sort of the same issue.... I was just gonna post a thread. All new grounds, yellow injectors, no vacuum leaks, all connectors tight... New fuel filter, pressure regulator... Getting frustrated. I don't have a tach but it seems like around the same rpm all the time.. Next plan is new cap/rotor/wires/coil. Plugs are new.. The tune up parts you're mentioning should be replaced with the plugs every 30,000 miles. Link to comment Share on other sites More sharing options...
xjrev10 Posted March 3, 2016 Share Posted March 3, 2016 I'm having sort of the same issue.... I was just gonna post a thread. All new grounds, yellow injectors, no vacuum leaks, all connectors tight... New fuel filter, pressure regulator... Getting frustrated. I don't have a tach but it seems like around the same rpm all the time.. Next plan is new cap/rotor/wires/coil. Plugs are new.. The tune up parts you're mentioning should be replaced with the plugs every 30,000 miles. Plugs are new. Painted over the others when I had the engine out a few weeks ago. I unplugged my TPS, started the truck and just got home from a 140 mile trip and it didn't act up once. So I'm debating on dropping the cash for a new one... Link to comment Share on other sites More sharing options...
Megadan Posted March 3, 2016 Author Share Posted March 3, 2016 Well, seeing as I have a new TPS it sounds like I may have to go over my TPS wiring again. Definitely can't hurt. Link to comment Share on other sites More sharing options...
cruiser54 Posted March 4, 2016 Share Posted March 4, 2016 Well, seeing as I have a new TPS it sounds like I may have to go over my TPS wiring again. Definitely can't hurt. Yup. Always set the TPS on the Engine side. Link to comment Share on other sites More sharing options...
xjrev10 Posted March 4, 2016 Share Posted March 4, 2016 So at day's end I'm About 200 miles with mine disconnected. When is it needed? Will it cause problems? Don't disconnect the battery? Spend $130 on a new one? Leaving for a 2 week wheeling trip next week and fuel prices are on the rise..... Link to comment Share on other sites More sharing options...
cruiser54 Posted March 4, 2016 Share Posted March 4, 2016 Why $130? Link to comment Share on other sites More sharing options...
xjrev10 Posted March 4, 2016 Share Posted March 4, 2016 That's what 2 different parts stores quoted me for a new one. 88 with a manual trans. Link to comment Share on other sites More sharing options...
cruiser54 Posted March 4, 2016 Share Posted March 4, 2016 That's what 2 different parts stores quoted me for a new one. 88 with a manual trans. See Post 8 in my Tips and save a boatload of $$. Link to comment Share on other sites More sharing options...
xjrev10 Posted March 4, 2016 Share Posted March 4, 2016 That's what 2 different parts stores quoted me for a new one. 88 with a manual trans. See Post 8 in my Tips and save a boatload of $$. I've read it 10 times. Are you saying it could be just out of adjustment? Or I will be able to see that it's bad before I buy a new one? I'm confused. Link to comment Share on other sites More sharing options...
cruiser54 Posted March 4, 2016 Share Posted March 4, 2016 That's what 2 different parts stores quoted me for a new one. 88 with a manual trans.See Post 8 in my Tips and save a boatload of $$. I've read it 10 times. Are you saying it could be just out of adjustment? Or I will be able to see that it's bad before I buy a new one? I'm confused. You need to hone your reading skills I guess. "For those with a MANUAL TRANSMISSION--the TPS for the manual transmission XJs is stupid expensive. You can substitute the automatic transmission TPS which is reasonably priced. The square 4 wire connector is just not used." Link to comment Share on other sites More sharing options...
xjrev10 Posted March 4, 2016 Share Posted March 4, 2016 Ok. You win. I was confused from the start so I didn't read the last paragraph. I'm still confused about it. So the new one for a auto comes with a different connector? Link to comment Share on other sites More sharing options...
cruiser54 Posted March 4, 2016 Share Posted March 4, 2016 Comes with 2 connectors. You only use one. Link to comment Share on other sites More sharing options...
xjrev10 Posted March 4, 2016 Share Posted March 4, 2016 Comes with 2 connectors. You only use one. All right. Thank you sir for all your help. Much appreciated. This thing has frustrated me to no end for the past few weeks. Link to comment Share on other sites More sharing options...
cruiser54 Posted March 4, 2016 Share Posted March 4, 2016 You'll get it figured out. Link to comment Share on other sites More sharing options...
Megadan Posted March 4, 2016 Author Share Posted March 4, 2016 Yep, my new TPS is a standard motor products auto trans unit. I cut off the extra connector and pigtail flush with the TPS and covered the ends with a little silicon just for a little added security. I got my hands on this one for $26 on sale, but the regular price on rock auto is about $35-ish. Link to comment Share on other sites More sharing options...
Rockfrog Posted March 4, 2016 Share Posted March 4, 2016 That's what 2 different parts stores quoted me for a new one. 88 with a manual trans. You also have the option to use a GM 2.8L TPS 86-94 ... Only requires swapping two wires around in the connector. In my parts it's the cheapest priced one about. Hell, if you go Standard and BWD rockauto has them cheap. Last I looked $32 cheap. I've been running the junkyard GM (delphi) sensor for the last 8 months or so now. Link to comment Share on other sites More sharing options...
xjrev10 Posted March 4, 2016 Share Posted March 4, 2016 Cruiser I ordered a new one today for $42. My truck actually has the 4 pin connector also in the harness. Always wondered what it was for. I suppose it's the same harness for both autos and manuals and that 4 pin is just not used in the manual trucks. I suppose I could plug it in for a cleaner look. Link to comment Share on other sites More sharing options...
Rockfrog Posted March 4, 2016 Share Posted March 4, 2016 They all had the 4 pin connector it was a standardized harness assembly. My 88 5spd has it as well. They just dead end is all. Link to comment Share on other sites More sharing options...
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