Modified 2.9 Cold run problems????

Mudiver · Aug 12, 2007

My 89 b2. has a modified 2.9.
PerformanceCam, Powermax heads, Pacesetter Headers. 58mm throttle body, MSD ignition, K&N air filter, Magnaflow dual exhaust.

Now my problem is this, When I first start up it runs fine. If I go about 1 to 2 blocks, It starts to spudder unless I floor it and then it's OK. It will run like this for about 4 to 5 minutes until it warms up. It seams to be in the first 60% of the peadle. Has any one had this problem before? This motor runs really good now and I can't even enjoy it. Please give me some ideas....

Thanks

southernlifttruck41 · Aug 12, 2007

If you figure this one out please let me know. My 88 ranger is doing the same thing. I put it on a computer and it said my temp. senser was bad. -40 degrees. I replaces it but it still runs like crap.

holyford86 · Aug 13, 2007

have you thought about pulling codes?

ford_2.8 · Aug 13, 2007

the oxygen sensor on my 2.9 made mine run like that the only way it would want to run is to the floor so maybe ur not gettin enough fuel now sence your gettin more air?

rickcdewitt · Aug 13, 2007

more air = less fuel

did you say it only does this while cold? when i put headers,throttle body,and K&N on my 2.9l it did wierd stuff while cold. i added a jet chip to richen up the fuel mixture and it went away. your 2.9l is speed density not mass air so it cant tell how much air its flowing when you modify it. i was thinking about swaping in the powermax heads and cam, is the power increase very big and did you lose bottom end torque(need to slip the clutch a lot more)?

Mudiver · Aug 13, 2007

rickcdewitt said:
did you say it only does this while cold? when i put headers,throttle body,and K&N on my 2.9l it did wierd stuff while cold. i added a jet chip to richen up the fuel mixture and it went away. your 2.9l is speed density not mass air so it cant tell how much air its flowing when you modify it. i was thinking about swaping in the powermax heads and cam, is the power increase very big and did you lose bottom end torque(need to slip the clutch a lot more)?

Thanks maybe that is when it started. It sure is breathing alot better now. Yes only when its cold. Then it runs fine. As for as the difference is uncomparable. When I'm in 3rd gear and between 3k and 4k rpms it really gets moving. Also before the rebuild top speed was about 80 to 85. Now top of 3rd gear will get me there and I still have 2 more gears. Just way to scary to go much faster in it for now. I'm fixing to start on the suspention. Then I will drive it like I stole it in the other 2gears.
THanks

Mudiver · Aug 13, 2007

ford_2.8 said:
the oxygen sensor on my 2.9 made mine run like that the only way it would want to run is to the floor so maybe ur not gettin enough fuel now sence your gettin more air?

Did it do it both hot and cold?
Thanks

MAKG · Aug 13, 2007

Huh? Speed density can tell how much air is in there. It's just the ideal gas law. You need to know the air charge temperature and pressure. There are direct sensors for both of those.

But we can't answer the original poster's question because it is modified. There are any number of F-ups that could be made. First question: is it rich or lean? Everyone seems to be assuming it's lean, but excessively rich mixtures will cause the performace problems described as well. Is the spark timing correct? How about the engine vacuum and compression? Are all the valves opening when they should? Are all the spark plugs firing? And so on.

Mudiver · Aug 13, 2007

holyford86 said:
have you thought about pulling codes?

Well, I took it to a mechanic a couple of months back and he could not get it to repeat. So I missed my chance on code running there. I will have to bring it back again to get some. I find if i baby it in the mornings it runs OK and does not fall on its face. I just started running it this way in the mornings and this helps. I guess that is why he could not get it to repeat. I guess in a sense with that said i'm probably flooding it in the mornings when I start it and this is why its running bad until it warms up. I did not know you could flood an EFI??

I will try to get codes ran..
Thanks

Mudiver · Aug 13, 2007

MAKG said:
Huh? Speed density can tell how much air is in there. It's just the ideal gas law. You need to know the air charge temperature and pressure. There are direct sensors for both of those.

But we can't answer the original poster's question because it is modified. There are any number of F-ups that could be made. First question: is it rich or lean? Everyone seems to be assuming it's lean, but excessively rich mixtures will cause the performace problems described as well. Is the spark timing correct? How about the engine vacuum and compression? Are all the valves opening when they should? Are all the spark plugs firing? And so on.

Well, I think you make a good point. I'm not a mechanic so this is why I come here. I think my problem is in settings as well. I think I just need to find me a speed shop and get this thing fine tuned. If I could do this I would probably wake it up alot more as well.
1. I think its running too Rich as well not to lean.
2. I would have to get a good setting for my distributor. Any input on how to obtain this will be appreciated.
Any info on other things I should check and where they should be would be a help as well.
Thanks'

southernlifttruck41 · Aug 15, 2007

Here is a red neck way to see if it is running to rich. If your tail pipe exit on the right hand side. Set your rearview so you can look at your exhust while it is running like crap. If it is putting out black smoke it is getting to much fuel. If the smoke is blue , you are burning oil, if your engine is blowing white it is water. Mine was running the same way . Mine was running lean. it was the ox senser. My wires were melted to the exhaust pipe. Hope that helped.

rickcdewitt · Aug 23, 2007

MAKG said:
Huh? Speed density can tell how much air is in there. It's just the ideal gas law. You need to know the air charge temperature and pressure. There are direct sensors for both of those.

But we can't answer the original poster's question because it is modified. There are any number of F-ups that could be made. First question: is it rich or lean? Everyone seems to be assuming it's lean, but excessively rich mixtures will cause the performace problems described as well. Is the spark timing correct? How about the engine vacuum and compression? Are all the valves opening when they should? Are all the spark plugs firing? And so on.

i guess what i ment to say was that speed density cant directly measure air flow with a sensor(mass air sensor) it uses the map and air temp sensor along with equations relating to a stock engine,it can get pretty confused when modified.i agree though,you want to make sure components work correctly before trying to tune them.mass air is more accomidating but it also needs tuning and/or chip if you take it too far.does anyone have dyno results of a modified 2.9l thats still usable in a 4x4 and the build specs for it?

Modified 2.9 Cold run problems????

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