Hey Guys,
Thanks in advance for any help you guys can offer! I searched 25 or so pages deep in this forum and didn't find the QA's that really fit my problem.
So here goes...
89' 2.8 116000miles
A few weeks ago it started bogging down real bad on initial acceleration. If I mash the gas it grabs, and runs fine. Once I'm up past 20mph or so it's fine. Stop again and go to accelerate and again it bogs down. No check engine light(it does work). It had a tune up a year ago, all but wires. So I replaced the wires. No help. Still no check engine light. When I unplugged the old MAF, the problem went away. So I replaced the MAF, MAF relay and the Air charge sensor. Still no help, in fact maybe worse.I was told thatwith the MAF unplugged it sent the car into "limp" mode which would make it run rich. So it seems to me the caris running lean for some reason. Am I way off?Any suggestions?With no check engine light, can a mechanic trouble shoot it or would it just be a guess?If it would throw a code my life sure would be a lot easier! Any help would be greatly appreciated.
Thanks!

 

Still clueless as to what could be wrong with it. I changed the distributor cap and rotor button and now it runs even worse than before.
Could barely get it away from the curb. Sputtering and backfiring like crazy. By the time I got it up to 2nd and 3rd gear it ran much better. I rechecked the plug wires to make sure I had them in the right spot. Checked out fine according to Hanes manual. The plugs were replaced about 18 months ago.
Any thoughts??

 

[X(] sick dog sorry for the lack of responses to your dilemma but heres just the correct lack of details and or consistancy maybe to keep most away. lets start with some basics does the ck eng lt illuminate with ignition on?? i think your realizing the same problem that most do with the new computerized cars, more often than not you cant throw a couple tune up parts at it and fix most of the minor problems. this is where finding a skilled mechanic you can trust will pay for itself in short order. not all things that can cause a newer car to run improperly are hooked to the computer. for some reason the public at large thinks that some magic code will pop out of the car anytime something doesnt work right and then you simply replace that part sorry it dont work like that. while these onboard diagnostic systems are getting better and better there are still large gaps in what they monitor and this is where the experience and training of the dreaded technician and subsequent bill come in. im not even gonna guess at the amount of dollars in un needed parts you've now replaced not to mention your time and inconvenience but i would think that it would have been cheaper to let those that know, DO. while there are bad shops everywhere dealers tend to be the most familiar and up to date with experience, tools and reference material. this should result in proper diagnosis and the least expense. as ive said here many times especially to those who want to get code readers for thier cars or know what code its throwin, the codes are merely a tool that will send a trained person in a direction it is still thier experience, training and knowledge that will ultimately diagnose the problem. if you have codes most shops will charge about an hour per code for diagnostics. if no codes are present no more than an hour or two should be charged to diagnose almost any problem (ask first dont assume) if the shop you chose wont guarantee something close to these rates, move on, they dont have the experience, tools or skills to do it right anyway. ill take a stab at a few things that come to mind for your car and due to mileage are things that should be checked or replaced anyway, catalytic converter, o2 sensors, bad vacuum lines, TPS, cts,map ???????? to name a few. with your skill level id highly recommend remaining the parts replacer but save yourself some time money and aggrevation and let those with the tools and experience make your life easier keep us posted kurt

 

Thanks for the reply,
The check engine light does work, and comes on whenI start the car, but goes right back off. We disconnected the TPS and it ran similar to when I disconnected the MAF. It seemed to smooth out some.
It's at the shop now. Unfortuneatly, they have had it two whole days and still havn't given me any estimates or diagnosis. tomorrow it's coming home one way or another. You are right, I am inexpereinced and probably should have just taken it straight to a pro, but I am stubborn!
What I really don't get is why the car would run so much worse after I changed the distributor cap and button??
I will post back when I get some answers, if for nothing else, maybe it will help someone down the road.
Mike

 

[&:] mike there is nothing wrong with inexperience or lack of knowledge, its those who dont at least attempt to gain either that are the worlds problems. im suspecting one of the sensors on the engine as you found out that if you disconnect one of them it puts the computer into a base program that is run by minimal inputs. let us know how it goes kurt

 

Im having a problem like this too. When i unplug my MAF, the engine runs better. It sputters at low throttle, especially bad when its cold. I had this problem in my turbo supra, but it was a cam position sensor. No distributor in that car. So maybe its related to the ignition? The car could be retarding the ignition when you unplug things and send it to limp mode. But i have no experience with the 2.8. Im trying to sell the car, and it has to be running right or im not trying to sell it.

 

[&:] sick dog and isphius, it was not uncommon to disconnect the MAF to test the MAF itself. if disconnected and car ran better it is often a bad MAF sensor , or wiring or connector or even computer, especially if it had a code pertaining to that circuit. sick dog had pulled a remove and replace on this component so it is obviously not that component but may still be in that circuit or any number of others. while i dont recommend it, this is where the financially challenged or just plain tight fisted individual might think about picking up some components at the junk yard to test in the vehicle(to be sure they work) and then stick on the shelf for later when a suspected component has failed. this has several advantages 1)used parts are usually cheap 2)normally cant return those expensive electrical parts to the auto store especially if opened or "test fitted" 3) has the potential to save money and down time for your ride isphius the ignition is definatly a possibility as its secondary side (spark producing components) are largely unmonitored by the on board diagnostics and therefore will usually have no codes set. the limp in mode doesnt specificly retard the ignition but it does limit power through fuel and rpm limits based on very limited inputs kurt

 

What do you mean by it limits rpms? how? because my car does shift unusually low. like 3900 or 4000 rpms. Its also making a code 34. Not quite sure on a solid definition of that or what could cause it. Also my fuel economy seems to go between low 15s to sometimes to mid 19s and back. Never in the middle. Could this be related to my code 34, lack of rpms, low power, etc?

 

[&:] isphius retarding the ignition has to do with the introduction of spark in the engines 360 degree rotation. the spark is introduced at tdc, advanced or retarded. in limp in mode a set program will limit rpms by dropping spark and or fuel to cylinders to limit power output. what year is your car?? your fuel economy seems a bit low unless your a lead footed individual. they placed the onboard diagnostics on the car for a reason along with the check engine light so if the light comes on it needs to be checked, running vehicles that have told you something is wrong can cause more damage and cost more $$$ if not checked right away. if your car is not running right and seems to be telling you as much it needs some attention. ill check on the code 34 but will need more info on car model , year etc kurt

 

[8D] isphius a quick check for code 34 would appear to be MAF related but need more info to be sure. the MAF was a problem child for gm vehicles for quite a few years kurt