Still sorting out things after H/C/I redo. It's hunting/surging at idle. Smoke tested, no leaks. Idle reset done. Will hold steady with spout out, but as soon as it's plugged in, the computer starts to do it's thing and timing goes from 12* to 20 BTDC and idle hunts between like 900 to 11/1200. This morning had pulled brake vacuum hose off for room to adjust clutch, and forgot to hook it back up. Car was idling like usual, but when I put brake hose back on............nothing changed. Take it off, put it on, no change. Pulling 14 vacuum at that port. I started looking for other easy vacuum ports, did the throttle body/valve cover.............zero. Opened the throttle a little, zero. What's possibly going on, especially the creating a big vacuum leak with no effect?
Any explanation?
- Thread starter dragstart
- Start date
Mcmahst
5 Year Member
I’m not sure your configuration, but most of the vacuum leaks, which don’t always show up in smoke tests, are the three vacuum valves for emissions/EGR. I also had a bad purge valve that caused a vacuum leak. If removing the brake hose doesn’t make any changes, you’ve got to have a leak.
Also, have you pulled codes? Most of us are so busy looking for the problem, we forget to do that. Good luck.
Also, have you pulled codes? Most of us are so busy looking for the problem, we forget to do that. Good luck.
All of the smog stuff was pulled by previous owner. I removed the egr . The only vacuum lines left are to A/C, fuel regulator, and the source line for the vacuum log on the firewall, and a vacuum source for an oil separator that comes off the manifold. And the way that works is PCV valve via hose to oil separator, then hose to vacuum source. Has aftermarket heads that have no provision for egr port, there's a spacer where the egr block was, the smog ports in the back of the heads are plugged. But you're right about not pulling codes, haven't done that. Everything worked before the H/C/I swap. (IAC, barometer, etc.) So not looking for codes for any of that, I guess that's next, but it would be coincidental if any of that failed at the same time all the swap stuff was done.
Mcmahst
5 Year Member
Also, and this is something else we don’t consider as often as we should; has anyone tested/repaired the ECU? I spent one year chasing a hunting idle problem that turned out to be a bad voltage regulator on the ECU board.
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These cars are at the point where the computers should be sent to ecuexchange first before trying to diagnose anything. Atleast open it and look at the circuit board for seaping caps and burn marks.
Codes should be able to be pulled with a Ford EEC4 scanner.
When the spout is pulled computer goes to preset conditions. Timing should be about that wiith it plugged in.
What camshaft and heads are on it ? Is it MAF or pre 87 ?
Codes should be able to be pulled with a Ford EEC4 scanner.
When the spout is pulled computer goes to preset conditions. Timing should be about that wiith it plugged in.
What camshaft and heads are on it ? Is it MAF or pre 87 ?
WhiteCobra95
10 Year Member
- May 2, 2006
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I think you have some really good suggestions here. To continue this line of thinking, here are some additional points and questions:
- If this is a speed density car? They don't react well to new camshafts or heads without tuning.
- If this is MAF car? If so, did you upgrade the MAF with the HCI build? Is it matched to the injectors or did you get get a chip calibrated for the new MAF and injectors?
- If it's the stock ECU, did it run fine before the HCI upgrade?
- What parts did you use in your build?
- You mention that your EGR system was removed. How did you do that... is it capped off? If it's not done properly, you cold have in internal EGR leak which can act like a bad vacuum leak.
- Have you tried capping off ALL of the vacuum connections to the intake manifold to see if the leak is coming from somewhere upstream?
- Have you tried bypassing the PCV system (e.g. run the PCV open to atmosphere by capping off both the PCV valve connection to the intake manifold and the fresh air feed to the valve cover), to make sure that you don't have a large leak from the crankcase (e.g. intake manifld to china rails or from a valve cover gasket / oil pan gasket leak)?
- If it idles fine with the spout removed, it seems like the PIP and TFI are working properly since it's stable at base timing, so it's most likely an air path issue where the IAC has too much range of authority (due to a leak) and the ECU is trying to control the idle by spark angle - like it's going in and out of a stall saver mode by advancing the spark to the high value you measured.
- Is there any chance that the timing ring on your damper has slipped and your base timing is more advanced than you are measuring?
- The ECU inspection suggestion from 90sickfox above is a great idea. Looking for any discoloration or burn marks would indicate something that's given up the ghost like a leaking cap or a fried trace / resistor. Opening it up for a quick look would be an excellent first step, then sending it out for a bench test / refurbishing would be the next level.
- Do you have any way to read out data from the ECU to check sensors? Did you replace the intake air temp sensor and coolant temp sensors when you did your HCI swap? I wonder if they're providing good temperatures measurements.
Maf, bought used 24lbs injectors with Complete CAI w/ mass air sensor which all was supposed to be in good order, taken off for a supercharger set up.
Stock ecu which was fine on stock engine.
Flotek 185 Thumper heads, Anderson N41, Eddy Performer, new lifters, rockers, timing set, etc.
Egr totally removed, no provision in heads for egr ports, spacer between Acufab 70 and intake, vacuum all capped.
I will bypass PCV as you suggest. AS it is set up now.....PCV valve to oil separator to intake vacuum.
I had thought the ecu was trying to control idle by timing, but once spout is connected it just goes to 20-21btdc and holds there. Initial timing is 12*btdc.
Damper is good, degreed cam, marks matched up.
Sensors new, ran KOEO codes, no sensor issues.
I had left the brake boost hose off after clutch adjust and started car.................massive 'leak', but no surge! I even drove car with SC port open, no low speed surge/bucking. Leads me to think it's an overfueling issue for that much unmetered air to be introduced and it actually makes things better.
Thanks for all the input!
Tried the PCV bypass today, the oil separator had a little oil in it, drained it while plugging up the vacuum source from the manifold. When I plugged the vacuum source for the oil separator, I was surprised that the engine slowed and died. Don't understand that one, Why would that happen?
89ripper
Founding Member
Started fine. Would the computer have a compensation factor for that air that gets pulled into the manifold that is unmetered by the MAF?
89ripper
Founding Member
To my knowledge it just causes weird idling issues, struggles against itself to keep running. Might be less of a factor under WOT.
Im not much of an expert with the ecu, ive recently (within last 6 years) had mine repaired, I was fighting my own problems with my car. I have one of the old alphabet cams in mine, she is quite tempermental!
WhiteCobra95
10 Year Member
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I'm really sorry for the late reply. I've been dealing with power outages at home from the storms that came through last Tuesday. It's been a rough week leading into the Labor Day weekend. Fortunately, things are mostly back to normal now and all of the downed-tree clean up is done.
It sounds to me like the issue might be the MAF sensor, which is not used during starts. It switches over to the MAF as the main load sensor just after the engine starts, and that's where it got rough again. I'm wondering if the MAF sensor is either bad or not properly matched to the injectors. Taking into consideration what you've stated above about how it runs better with a large leak, like from the brake booster hose being left open, it seems like adding a large amount of un-metered air flow gets the sensors air flow reading shifted closer into the zone where it should be.
I didn't want to suggest throwing parts at it and this could be really not fun if it doesn't work, but do you have your stock MAF and induction system from air box up to the throttle body and the original 19 lb/h injectors? You could try reinstalling these parts to see if things clear up with known good parts that match the calibrations in the ECU. (I know, re-installing the injectors is a huge pain and I apologize in advance if this doesn't resolve the problem.) This would help confirm that something isn't right with the MAF / injector combination, and shouldn't be a problem for starts, idle, and light to mid-load driving to rule out this possibility. You would also need to unplug the battery for a bit to clear out any ECU adaptations made with the current hardware.
You could also try starting and idling with the MAF unplugged to use the TPS as the main load sensor and see if it's any better. You'll probably be on the rich side since you've got bigger injectors than the ECU expects, but it might tell us something if it runs any better than it does with the MAF plugged in.
A less intrusive option would be to check the part number of the MAF sensor itself with the manufacturer. We need to make sure that it's transfer function is tweaked to compensate for 24 lb/h injectors with your specific ECU. I'm thinking that the previous owner may have had a custom chip or custom ECU calibration with the correct TF data for this MAF, and it's either not a shifted MAF for 24 lb/h injectors or just a high flow range sensor. This is just a theory based on everything you've posted and the conclusion that you've already confirmed that there are no leaks in the system.
It sounds to me like the issue might be the MAF sensor, which is not used during starts. It switches over to the MAF as the main load sensor just after the engine starts, and that's where it got rough again. I'm wondering if the MAF sensor is either bad or not properly matched to the injectors. Taking into consideration what you've stated above about how it runs better with a large leak, like from the brake booster hose being left open, it seems like adding a large amount of un-metered air flow gets the sensors air flow reading shifted closer into the zone where it should be.
I didn't want to suggest throwing parts at it and this could be really not fun if it doesn't work, but do you have your stock MAF and induction system from air box up to the throttle body and the original 19 lb/h injectors? You could try reinstalling these parts to see if things clear up with known good parts that match the calibrations in the ECU. (I know, re-installing the injectors is a huge pain and I apologize in advance if this doesn't resolve the problem.) This would help confirm that something isn't right with the MAF / injector combination, and shouldn't be a problem for starts, idle, and light to mid-load driving to rule out this possibility. You would also need to unplug the battery for a bit to clear out any ECU adaptations made with the current hardware.
You could also try starting and idling with the MAF unplugged to use the TPS as the main load sensor and see if it's any better. You'll probably be on the rich side since you've got bigger injectors than the ECU expects, but it might tell us something if it runs any better than it does with the MAF plugged in.
A less intrusive option would be to check the part number of the MAF sensor itself with the manufacturer. We need to make sure that it's transfer function is tweaked to compensate for 24 lb/h injectors with your specific ECU. I'm thinking that the previous owner may have had a custom chip or custom ECU calibration with the correct TF data for this MAF, and it's either not a shifted MAF for 24 lb/h injectors or just a high flow range sensor. This is just a theory based on everything you've posted and the conclusion that you've already confirmed that there are no leaks in the system.
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