Having another issue with the wife's 2000 Protege 1.8. A few months ago she had a leaking intake manifold gasket. The dealership repaired that one twice before getting it right. Now this week another issue has started.

The engine idles fine. Runs fine at speed but when accelerating from a stop it stumbles badly. Way worse with the AC running obviously it puts more load on the engine.

I have found a few possible causes on the boards. Possible leaking air intake hose. Possible timing belt worn. Plug wires (I would think it would have a miss at any RPM though)

I'll run a compression test to see if the timing belt has slipped and caused a valve timing problem. I would think it would have poor idle and at speed acceleration with this one though.

No ODBII codes are being generated.

Any other ideas? EGR, other sensors?

Thanks!!!

 

Have you considered fuel starvation? If the engine is stumbling but you get no misfire codes (plus a CEL) then it seems that ignition is OK. You've checked for "sneak air" between the MAF sensor and the throttle, and that appears OK, so the next obvious thing would be to verify that you haven't got fuel pressure or injector issues. This is also consistent with things being worse with AC on, since the added load increases the required fuel flow rate.

 

I thought about fuel starvation. It could be the pump going bad or filter/strainer. I would think it would have trouble accelerating at higher speeds as well. I'm going to pull the plugs and see if any of them look rich or lean. Thanks for the response. I'm going to look it over this weekend and see if I can find anything else wrong. I'll test fuel pressure too.

 

Update. I had the wife fill her fuel tank and then I added a good dose of Lucas Oil Fuel Injection Cleaner. Yesterday she drove on the highway and called me this morning to tell me the problem has cleared up. So maybe it was just some dirty injectors. I'll add more cleaner on the next fill up. I USUALLY add some about every 6 months so it was due anyway. Hopefully that's all it was.

 

I guess I spoke too soon. Wife told me yesterday afternoon that the car is still having the same problem. She thought it was doing "better" but it's not. Back to plan A. Check, test and inspect everything. I did get a chance to inspect the intake hose and do not see any cracks.

 

I haven't experienced it, but people on this forum have mentioned fuel issues caused by injector contamination due to corroded and flaking downstream fuel lines which are located beyond the fuel filter (integral with the fuel pump near the tank).

 

Found a loose vacuum line under the throttle body. I also checked the spark plugs. They looked well worn so I I changed those. I had replaced them about 40k miles back with NGK's I bought Autolite this time. I ordered new wires too and will put them on tomorrow if they come in. The engine is running better than it has in quite a while. No bog or hesitation.

 

I would like to see the pics. of your work. It seems you are doing a nice job.