IAC problems

[bhamdale]

2006 chaparral 5.0 gxi-e, running fine went to neutral and boat dies wont crank up
i can shift to fast idle cranks and runs smooth at higher rpms but dies in neutral.
replaced IAC cranks but idles at 1200 rpm.
read were test light should flash on all 4 wires to IAC, 3 wires flash. Blue with yellow tracer dead
any thoughts? thanks

 

[Scott Danforth]

Get factory manual for your serial number and follow the trouble shooting tree in the manual

 

[alldodge]

If I understand correctly

It was running fine until it wouldn't idle and would die. Could get it started with fast idle.

replaced IAC cranks but idles at 1200 rpm.

After replacing the IAC it now will start but idles at 1200 RPM?
If this is true, I would suspect the IAC was not installed correctly, or the wrong part was installed

What is the motor serial number and what is the part number for the IAC?

 

[bhamdale]

Get factory manual for your serial number and follow the trouble shooting tree in the manual

I did. The manual gives wiring diagram and a flow chart, i followed it until i got to the last question ... do all 4 wire blink with test light? the answer then is verify repair. No yes or no option follows

 

[bhamdale]

If I understand correctly

It was running fine until it wouldn't idle and would die. Could get it started with fast idle.


After replacing the IAC it now will start but idles at 1200 RPM?
If this is true, I would suspect the IAC was not installed correctly, or the wrong part was installed

What is the motor serial number and what is the part number for the IAC?

Yes boat runs great at any throttle position other than neutral or idle. IAC has 2 screws and 1 oring and 1 connector. I made sure old oring was removed. No vacuum leaks. I replaced IAC with volvo penta IAC but dont have part # with me. motor serial #4101216623.

 

[Scott Danforth]

Remember one of the wires is a ground

The factory manual tells you what you should read on every line

 

[alldodge]

So when you said

replaced IAC cranks but idles at 1200 rpm.

Means it does same as before IAC was replaced. You have to keep the idle up around 1200 to keep motor running

 

[bhamdale]

Remember one of the wires is a ground

The factory manual tells you what you should read on every line

would you please send me voltage chart. 4 wires (1) pin16 bl/y to D, (2) pin 31 p/bl to c, (3) pin 30 bn/gr to b, and (4) pin15 gn/sb to A. According to manual and corrected charts from volvo. Per manual spec all 4 wires to IAC from ecm are positive voltage, ground is also controlled thru ecm, Which I am afraid is were the problem is going to be. ECM very costly so just checking all my basis before ordering. thank you for sticking with me.
I'm an automotive mechanic and this system is an 98 gm system. I have tested grounds, power and reference voltage.

 

[bhamdale]

So when you said

Means it does same as before IAC was replaced. You have to keep the idle up around 1200 to keep motor running

no, sorry. before replacing IAC it would crank no start. New IAC it cranks and starts just idles high, 1200rpm. Checked for vacuum leaks because that was my first thoughts.
multiple places I have read that all 4 wires to IAC should blink with test light. 3 out of 4 are blinking, one blue /yellow nothing.

 

[alldodge]

I don't have the E version but this is what I have for C/D for IAC

 

[QBhoy]

I don’t think it’s the IAC at all. They almost always show an audible alarm when they fail on these.
I’d be looking towards other things like the TPS or camshaft sensor. Get it plugged in though.

 

[alldodge]

Weird issue for sure. No start and after IAC replaced it does start but idles at 1200

Agree with your test procedure, should blink with each connection as manual shows

One test is turn engine OFF, unplug IAC for 10 seconds. When restarted does it idle 200 rpm higher?

 

[Scott Danforth]

Old IAC could have been totally open. New IAC could have been partially open.

There are 4 wires 2 are hi, 2 are low (ground ref)

IAC should move to close with key on and engine is over 100F

 

[bhamdale]

no, sorry. before replacing IAC it would crank no start. New IAC it cranks and starts just idles high, 1200rpm. Checked for vacuum leaks because that was my first thoughts.
multiple places I have read that all 4 wires to IAC should blink with test light. 3 out of 4 are blinking, one blue /yellow nothing.

worried it may be ecm. one answer from "just answer" said when IAC goes bad 10-15% of the time it blows the ECM.

would you please send me voltage chart. 4 wires (1) pin16 bl/y to D, (2) pin 31 p/bl to c, (3) pin 30 bn/gr to b, and (4) pin15 gn/sb to A. According to manual and corrected charts from volvo. Per manual spec all 4 wires to IAC from ecm are positive voltage, ground is also controlled thru ecm, Which I am afraid is were the problem is going to be. ECM very costly so just checking all my basis before ordering. thank you for sticking with me.
I'm an automotive mechanic and this system is an 98 gm system. I have tested grounds, power and reference voltage.

I don't have the E version but this is what I have for C/D for IAC


View attachment 367417

That is it. I have tested for continuity and shorts all is good, just trying to figure out what drives the d circuit bl/y to pin 16. I'm afraid its going to be the driver in the ecm. ecm is $2000. just trying to make sure I'm not missing something simple. Thank you for your time, this forum has been extremely helpful

 

[alldodge]

No expert, but pins B and C are listed as switched. This tells me the ECM grounds those pins to energize the coils. Meaning the other pins have full power when ECM is powered up. The test light will flash because ECM is switching on/off which will cause the like to flicker on either side of the coil

Looks like a ECM issue but I would send it for testing before buying another. OBDiagnostics (Bob) or Boats Unlimited (John). Would be good to get input from @muc if he has time

 

[muc]

Hard to comment on this one, being asked to condemn the ECM is big $$$$. I’ve never made a mistake on this, but have had to pick up the pieces when another tech or customer has. Never a good outcome when that happens.

Really would like more info.

Serial number 4101216623 isn’t recognized as a good serial number by Volvo. What is the serial number?

No mention of scan results. Have you scanned the engine?

Correct test is to use a 4 terminal 2 light noid light. If you’re using a volt meter, are you connecting one of the leads to power or ground? Or testing between the 4 wires?

The “E” series motors didn’t have the greatest documentation.

What service manual are you using?



That said, looks like a MEFI 4 multi-port engine. If so ---- all 4 wires going to the IAC are at battery voltage and all of them switch between batt positive and batt negative. But they do it in pairs.

 

[bhamdale]

Hard to comment on this one, being asked to condemn the ECM is big $$$$. I’ve never made a mistake on this, but have had to pick up the pieces when another tech or customer has. Never a good outcome when that happens.

Really would like more info.

Serial number 4101216623 isn’t recognized as a good serial number by Volvo. What is the serial number?

No mention of scan results. Have you scanned the engine?

Correct test is to use a 4 terminal 2 light noid light. If you’re using a volt meter, are you connecting one of the leads to power or ground? Or testing between the 4 wires?

The “E” series motors didn’t have the greatest documentation.

What service manual are you using?



That said, looks like a MEFI 4 multi-port engine. If so ---- all 4 wires going to the IAC are at battery voltage and all of them switch between batt positive and batt negative. But they do it in pairs.

The engine was scanned with no codes present.
The engine # is off of my registration, it didn't match when I tried to use but was the only number I had, so I'll have to go back to marina and get good number.
I didn't check voltage on 4 terminal of IAC valve just test light checking for blink per manual.
The manual I'm using is workshop manual EFI diagnostics C2(0). I downloaded it. It doesn't list the E engine designation but all wire colors and pins and connectors match.
I really appreciate your help

 

[bhamdale]

I don’t think it’s the IAC at all. They almost always show an audible alarm when they fail on these.
I’d be looking towards other things like the TPS or camshaft sensor. Get it plugged in though.

I agree. The IAC can't operate properly if it's not getting signal from all the wires. The blue /yellow wire is not getting any voltage from ECM. If I could just figure out what controls that wire problem could be solved. Like automotive manuals what happens inside the ECM is a mystery.

 

[bhamdale]

Hard to comment on this one, being asked to condemn the ECM is big $$$$. I’ve never made a mistake on this, but have had to pick up the pieces when another tech or customer has. Never a good outcome when that happens.

Really would like more info.

Serial number 4101216623 isn’t recognized as a good serial number by Volvo. What is the serial number?

No mention of scan results. Have you scanned the engine?

Correct test is to use a 4 terminal 2 light noid light. If you’re using a volt meter, are you connecting one of the leads to power or ground? Or testing between the 4 wires?

The “E” series motors didn’t have the greatest documentation.

What service manual are you using?



That said, looks like a MEFI 4 multi-port engine. If so ---- all 4 wires going to the IAC are at battery voltage and all of them switch between batt positive and batt negative. But they do it in pairs.

the boat would crank but not start with old IAC, once I replaced the IAC it will crank and start just idles to fast 1200 rpm. Do you think the bad IAC could have shorted the ECM driver on pin 16?

 

[bhamdale]

Hard to comment on this one, being asked to condemn the ECM is big $$$$. I’ve never made a mistake on this, but have had to pick up the pieces when another tech or customer has. Never a good outcome when that happens.

Really would like more info.

Serial number 4101216623 isn’t recognized as a good serial number by Volvo. What is the serial number?

No mention of scan results. Have you scanned the engine?

Correct test is to use a 4 terminal 2 light noid light. If you’re using a volt meter, are you connecting one of the leads to power or ground? Or testing between the 4 wires?

The “E” series motors didn’t have the greatest documentation.

What service manual are you using?



That said, looks like a MEFI 4 multi-port engine. If so ---- all 4 wires going to the IAC are at battery voltage and all of them switch between batt positive and batt negative. But they do it in pairs.

I found this in manual tonight, wish I was better at computers so I could post the function test diagram.... anyway
Step 4 using test lamp connected to ground, probe each of the 4 IAC harness terminals. Does the test lamp blink on all 4 terminals:
yes= Step 5 IAC circuit functioning properly replace bad IAC,
no= Step 6 locate and repair poor connection, open, or shorted circuit that did not blink
Step 8 replace faulty ecm