Tuning Question
Thread Starter
4th Gear
Joined: Apr 2010
Posts: 4
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From: Cypress TX
Tuning Question
I'm working on a 1986 with a 4+3 transmission that I believe is having Cold Start Injector (CSI) issues. I would like to do away with the CSI all together. I've read that the 1989 ECM PROM (6E mask) did away with the CSI by allowing the other 8 injectors to provide the extra fuel needed in a cold start condition. I've also read that the 4+3 transmission was not available int 1989. So, my question is this, does the 6E mask still have provisions for the 4+3 transmission or would I need to use the stock 1986 (32 mask) and make fuel richness adjustments during cold start conditions? I'm new to tuning and hope this is not a silly question. I've conducted many searches on the web and have read through the forums here to try to find an answer, but I have been able to find anything yet. Any help would be greatly appreciated.
Thread Starter
4th Gear
Joined: Apr 2010
Posts: 4
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From: Cypress TX
Thanks for the reply bjankuski! I figured that would be the easiest solution, but I wanted to run it by the experts before I fudged something up. Ok, another newbie question: from what I've read, I believe the ECM runs in an open loop when the engine is cold and moves into a closed loop when it warms up. Are there separate injector settings for open/closed loops or would an injector Base Pulse Width (BPW) adjustment be the best place to start?
Instructor
Joined: Mar 2009
Posts: 230
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Before you do that are you sure you are getting cold start fuel pressure. I thought I was having same problem till I heard my fuel pump taking a couple of cranks to energize . Fuel pump relay needed replaced.It was taking too long to get signal from computer that I had sufficent oil pressure .Fuel pump will not work if oil press is low ,controlled by ECM and relay .You can eliminate the 9th inj. and never have start problems. alot of guys here, from what Ive read, do it
Thread Starter
4th Gear
Joined: Apr 2010
Posts: 4
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From: Cypress TX
Thanks for the heads up chrisr0315. I originally had a bad fuel pump and was not getting any fuel pressure at all. I changed the fuel pump, strainer and fuel filter.I now get get good fuel pressure when turning the key on (I don't remember for sure how much, but I think it was around 40 psi). The problem I'm having now is that when started cold, the car idles horribly. The only way to keep it idling is to occasionally pump the gas when it is about to die. When the temperature reaches around 110 degrees, the car idles/runs good. I tested the ohms on the IAC and It appears to be ok. This is what makes me think it is a Cold Start Injector problem.
Melting Slicks
Joined: Aug 2003
Posts: 3,389
Likes: 391
From: Lakeville MI
The CSI is only intended to provide supplemental fuel during cranking. It is not intended to provide extra enrichment when the car is running.
Start-up enrichment fueling and open loop fueling vs coolant temperature handle this.
The rough running during warm up is an open loop fueling issue, could be due to many things....coolant temp sensor, MAF, injectors, vacuum leaks, fuel pressure...anything that can lead to mixture errors.
Scanning is the only way to really determine what is going on if you have a bad input or mechanical problem that is leading to the rough running.
Note: The 89 tunes permit twice the maximum crank fueling pw as compared to 86, 87 and 88.
This can also be changed in the 86, 87 and 88 bins as already mentioned, but you need to adjust the crank pw scalar as well as the crank fueling table to achieve 89 like crank fueling. This may not be common knowledge.
Start-up enrichment fueling and open loop fueling vs coolant temperature handle this.
The rough running during warm up is an open loop fueling issue, could be due to many things....coolant temp sensor, MAF, injectors, vacuum leaks, fuel pressure...anything that can lead to mixture errors.
Scanning is the only way to really determine what is going on if you have a bad input or mechanical problem that is leading to the rough running.
Note: The 89 tunes permit twice the maximum crank fueling pw as compared to 86, 87 and 88.
This can also be changed in the 86, 87 and 88 bins as already mentioned, but you need to adjust the crank pw scalar as well as the crank fueling table to achieve 89 like crank fueling. This may not be common knowledge.
Thread Starter
4th Gear
Joined: Apr 2010
Posts: 4
Likes: 0
From: Cypress TX
Thanks for the CSI information tequilaboy. I was under the assumption that the CSI would continue to inject additional fuel until the engine warmed up. Thanks for clearing that up for me. I will order the hardware needed to scan the system for any irregularities. I was planning on using TTS Datamaster. Is this a good software are are there better alternatives? I would still like to eliminate the CSI in the near future. I'm sure this has been done by many others in the past. Can anyone point me to a post/article that can explain the process in detail? This will be the first time I've attempted to do any tuning and I'm trying to get as much information as I can so I don't jump into it blindly. Would it benefit me to get the bin from an 89 and compare it to the 86 so I could set up the 86 similarly?
