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HELP!!!! 91 spirit 2.5 tbi (non-turbo) bog down issue


the mitch
06-18-2008, 04:54 PM
I have a 1991 spirit, 2.5L automatic 3 speed TBI non turbo model. When the engine is cold, it wants to "bog down" as if it is trying to haul a semi trailer behind it. When the engine is warm, it runs flawlessly without issues. When it is cold and does it, which is all the time for the first 20 minutes or so of driving, it's powerless. It sounds like an old broken down helicopter trying to take off, but a lot quieter. New spark plugs, new dist. cap/rotor, new map sensor, new fuel filter. I have reset the computer. The check engine light has never came on even before resetting it. I've only had it for 2 years, and it only has 53k original miles on it now. I put 25k on it in 2 years. It got me accross the country twice without any issues, even at 3.5k rpm for 9-11 hours straight doing 70-75 mph. Now it's doing this after it hasn't seen highway use in months, and yes, i do "hot rod" sometimes to blow the junk out of it, and no I never have redlined it. I go through fuel filters like a fat kid does cake. One a month or it looks like lipton iced tea and you can't even blow through it. Passed emissions testing on a cold start with flying colors. It's eating gas badly. I'm getting 9-12 mpg on a good day. 165 miles to full tank because of this!!! No error codes. Computer registers like nothing has ever gone wrong with car. Hell, the coolant is over a year old and still looks brand new, with new water pump last year of course. The engine never even hits normal temp, and i have 70% water, 30% coolant. thermostat is a month old, and always has ran this chill even with previous thermostats.

cold = bog out .. if in neutral and revved a little, it putters on the return to idle

warm = runs perfect like the day it came off the showroom floor.

I'm so confused and broke now trying to fix my one and only car. I cannot afford much and I am trying so hard to make ends meet. If this thing happens to blow up on me, I'll be homeless. Fresh start on new life. I can't take anymore stress.

the mitch
06-18-2008, 07:22 PM
Apparently, the coolant temp sensor sitting right under my thermostat changes the a/f mixture? wtf? i did not know this considering I do all of my repairs myself, because mechanics are a ripoff. I will get a new one (10 bucks, was thinking more), this weekend and replace it. just a simple 30 second job. I'll post a reply if it worked. Oh, and any ideas on a way to clean the gunk out from below my throttle body? I looked inside down below the butterfly valve (unsure of technical term) and it was pretty chunky. A mirror and flashlight showed more chunkiness. A neon green pipe cleaner shoved down in there until it stopped looked like it would if you haven't cleaned your pipe out in years. thick and gunky. I threw some lucas fuel system cleaner in it hoping it works.

I have to add this sensor is factory age at almost 18...

KManiac
06-18-2008, 07:37 PM
Have you checked your fuel pressure at the throttle body? A bad fuel pressure regulator will cause an extra rich mixture and massive fuel consumption. But you wouldn't see this at the tail pipe because the cat is working overtime to burn up the excess fuel.

Check your fuel line pressures and let us know what you find. Look, too, at the vacuum hose to the fuel pressure regulator and make sure it is connected and not leaking.

the mitch
06-18-2008, 07:52 PM
When the engine is running cold, I do hear a fast paced ticking noise coming from it, but have no way to measure pressure. With current funding and tools, I can only tell you if it shoots out of the lines. The ticking is repetitive at the same pace, but pretty noisey. You can only really hear it with the hood open and the air filter off. When warm, it does it, but very quietly. BTW, flowmaster cat and enlarged exhaust with flowmaster muffler, all 3 months old. stimulus baby. If it helps, when cold and acting the way it has been acting, I do see a small amount of carbon shoot out the back, acting like it's clogged, when I know it's really not. I didn't spend 1500 bux on that exhaust work, including custom 4-2-1 exhaust headers for it to clog in 3 months. I had it dyno'd at an old friend's shop who did it all for free and got 161.23 hp out of it. :) .. now it gets like, .23 ......

KManiac
06-19-2008, 10:35 AM
The ticking noise you hear is the tbi injector working as designed (situation normal). The soot coming out the tailpipe is an indication of excess fuel discharge (snafu). Again, I suspect a faulty fuel pressure regulator, which is allowing too high a fuel line pressure at the injector and causing a richer mixture and high fuel consumption. Remember, too, that when the engine is cold, the computer compensates by allowing a richer mixture until warm. So when you enrich an already rich mixture, your engine will run like a carbureted engine with the choke stuck closed! Sound familiar?

There should be a port on the fuel supply rail that will allow the connection of a pressure gauge to measure the line pressure. Fuel pressure test kits are available at most auto parts stores. I seem to recall that the fuel line pressure at idle in the tbi engine should be 39 psi, but don't' quote me on this. Look it up in a manual to verify. Make sure, too, that the proper vacuum line is connected to the fuel pressure regulator and that it is not damaged or leaking.

Let us know what you find and what you do.

the mitch
06-19-2008, 04:23 PM
Dang, you're good. 39 PSI is right on the money. Speaking of money, I'm gonna shell out the money for the pressure check tool, coolant temp sensor, AND I remembered my parents have the exact same car with engine (different interior), and I will play around with different parts, including the regulator. Just 2 more days to go until I do this. The problem is consistently getting worse though. Today, I shot out a HUGE cloud of black smoke on startup (small rev, 10 sec. after start). Jet black, smelled like straight gasoline. Stuck to the grass at work to. It only did it once and then stopped, but puttered longer than usual.

the mitch
06-20-2008, 05:45 PM
12 - Description: Memory standby power recently lost
Power loss light: Off
Limp-in mode: None

...I need a new battery, trust me on that. It's 13 years old and somehow still works. It's not even leaking.

17 - Description: Engine stays cold too long
Power loss light: Off
Limp-in mode: None

...Now, I been through a lot of thermostats, and no way can I get it to run warmer, even using 70water/30coolant. It just stays really cold. Every car from my old jeep, to my 1989 Lincoln ran cold to. Maybe I just have luck with engines not overheating? New coolant sensor installed right after work today .. took 30 seconds .. will tell you if it worked tomorrow. It did change the temp reading on the dashboard, but not by much. Is it the water pump? It's still 3 months old after the old one crapped out. Does it need to "break in"?

51 - Description: Oxygen sensor (http://www.knizefamily.net/minimopar/ecu/oxygen_se.html) output indicates lean too long
Power loss light: Off
Limp-in mode: Engine allowed to run rich, but prevented from running lean

... Getting new o2 sensor and wiring tomorrow. Hope it works. I found a place to make my own fuel pressure tester, and I have the stuff to do it right at home, but am lazy, so I might just rent one.

New battery and codes cleared from system. It was still a warm start, so I don't positively know for sure if it worked, but it idles as smooth as a baby's bottom (for) now. Acceleration dramatically improved without hesitation.

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