Hey Guys,
Newbie here, at least to posting! I have this topic posted over at gen tech and not having any luck there so I thoughtI'd try it here.
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!

Update-
I changed the distributor cap and rotor button and now it runs even worse. Sputtering and backfiring, I could barely get it away from the curb. it runs better once it gets up past 20mph or so. But from a dead stop it is real bad. I checked the wires for correct position and they matched up according to haynes manual. I'm totally lost now.
Any thoughts?

 

Unplugging the MAF will make the mixture a little richer initially, but the O2 sensors will bring it back. More important, unplugging the MAF will force the system in open loop mode, and ignore most of the sensors. Being that it ran better with the MAF unplugged it is a good indication of a sensor problem. Take a good look at the O2 sensor/s with a scan tool and see if the voltage is changing up & down rapidly as it is supposed to. With a scan tool, not a code reader, you can look at the output of all the sensors and see if the are telling the truth or lying, and makes no difference if the trouble lite is on or off.

 

my 89 RS has that same problem!, sputters like crazy unless I floor it, my mechanic had no idea how to fix it, or didnt care.... lemme know if you find the problem, ill tell you if i make any discoveries....

 

Check the voltage of the throttle body sensor on the butterfly valve. I had that problem, then I find that unplugging the sensor and wiring it so that I could fit in a multimeter, I had to loosen the sensor off the throttle body and adjust it to 4.0 volts (I think?? check chilton's) and the problem went away.

 

It could be a lot of things but you might was to check for a stuck EGR valve. The EGR valve should only be open when the car is under load. It allow exhaust gas to mix with your clean air/fuel once the car gets going. Sometimes they get gooped up and do not close. It will cause very bad idle and a very bad acceleration. I have had customer get their cars towed in cause they thought the motor was blown. How bad it is depends on how far stuck open the valve is. You can tap the side of the EGR valve. Best thing to do is pull it off andand look at the underneath, see if it is sealed. Check with some carb cleaner. once your sure its sealed reinstall and DO NOT connect vacuum, plug it. Start the car. If the car is better reconnect the vacuum.If it goes bad again replace the valve.